# 137 De Koven Street, 8 October 1871 — block geometry, buildings, witnesses' positions, conditions

Every downloaded file is logged in `SOURCES.md` (file | URL | fetch time UTC | note).
Coordinate table: `plan/plan_coordinates.csv` (generated by `plan/plan_coords.py`); digitised Musham plan: `plan/musham_plan_digitized.csv`;
scaled drawing: `plan/block38_plan_1871.png` (NOT a survey — a drawing of the numbers below, 4 px/ft).
All "plan" coordinates: **x = feet east of the 1871 east line of Jefferson St.; y = feet north of the north line of De Koven St.** (the SW corner of Block 38 = origin).

Conventions on resolution: *survey plat* = a recorded subdivision dimension (good to 0.1 ft); *atlas* = a lithographed real-estate atlas
(Greeley-Carlson 1891) or Sanborn 1906 read at 4-5 px/ft (±1-2 ft); *sketch* = Musham 1940 plan / Andreas text (±2-5 ft); *estimate* = my inference, basis stated.

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## 0. Ten-line summary

* The O'Leary property was the **east half of Lot 12, Block 38, School Section Addition** (Michael McDermott's affidavit of 15 Oct 1871, quoted in Andreas II:708: "at No. 137 DeKoven Street, on the east half of Lot 12, in Block 38, School Section Addition"). Lot 12 is 50 ft wide, so the parcel is 25 × 100.75 ft, its west line **133.4 ft** and east line **158.4 ft** east of the Jefferson line (survey-plat dimensions, see §1).
* Block 38 was platted 358 ft E-W (1833 School Section plat, column label) and originally 396 ft N-S; the 15-ft alley was opened in 1855 "on the N. ¼ line" (99 ft south of Taylor); De Koven St (60 ft) was cut through the original block; the south side of De Koven (lots 15-21) is therefore also Block 38.
* Numbers step 2 per 25-ft half-lot on both sides: north side 141 = E½ 13, 139 = W½ 12, **137 = E½ 12**, 135 = W½ 11, 133 = E½ 11 …; south side 140 = H-lot 2, 138 = H-lot 1, 136 = W½ 18, **134 = E½ 18 (Catherine Sullivan, Daniel Sullivan's home)**, 132 = W½ 19, **130 = E½ 19 (William White)**, 128 …
* Barn: 16 × 20 ft, 14-16 ft high, at the alley end of the lot; O'Leary cottages (double, 36 ft N-S total, ~16 ft wide) at the street end; Dalton's one-storey cottage (135) on posts 4 ft high, on his west lot line, front 38-40 ft back, 40 ft deep, with an 8-ft board fence from house to his 12×20 shed at the alley.
* From the front of White's lot (x 233-258, y −60) every straight line to the barn crosses Dalton's lot between y = 38 and 78 (see §2.6 table) — i.e. passes through the Dalton house footprint unless the flames were seen above its roof. From the front of Sullivan's own house (x 183-208) the lines to the barn's west half clear Dalton's house but cross the O'Leary rear cottage / yard.
* Modern anchor: Cook County parcel 17-16-324-029 (Fire Academy) still carries the 1835/1874 lot-line vertices; its west edge is 18.3 ft east of the 1871 Jefferson line and its east edge 20.1 ft west of the 1871 Clinton line (Jefferson and Clinton were widened from 40 ft to ~74-75 ft; Taylor from 60 to ~80 ft; De Koven unchanged at 60 ft).
* The barn site (x 133-153, y 85-101) falls in the open yard immediately north of the Fire Academy's front wing (rear wall at y ≈ 80.6); the "Pillar of Fire"/"Tongues of Flame" sculpture stands on the plaza at the NE corner of De Koven and Jefferson, roughly 90-120 ft WSW of the barn site.
* Weather (Signal Service, Chicago, via Musham 1940 and NWS): 7 a.m. 51 °F, SW 19 mph, RH 62 %; 2 p.m. 85 °F (unofficial), SW 35 mph; 4 p.m. 79 °F, 22 mph, clear; sunset 5:30; wind fell to a "gentle breeze" by dark and "the same gentle breeze … from the southwest" at 9 p.m.; a 60-mph anemometer reading near midnight is dismissed by Musham as instrument error. Rain since 3 July 1871: 1.40 in (Musham/Andreas) — 3.55 in for 7 Jul-8 Oct per NWS (≈8 in below normal); none 29 Sep-8 Oct.
* Not obtained (blocked or unavailable): Bales 1997 article and 2002 book text (only Google-Books snippets); the Andreas premises plat cited in the report (not on pp. 708/709/714/716 fetched here); 1870 (13th) and 1872 (15th) Edwards directories; NCEI/NOAA original Signal Service forms; HathiTrust, Chicago Collections, CHM image server (Cloudflare).

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## 1. Block subdivision, lots, alley, streets, coordinates

### 1.1 Plat history (Greeley-Carlson *Atlas of Chicago* vol. 1, 1891-92, plate 27 margin notes and plate 28; Northwestern Univ. IIIF copies in `atlases/`)
* **"A"** — "Map of School Sec. 16, T. 39 N., R. 14 E. of the 3rd P.M. … Surveyor's certif. dated March 15, 1833" (`atlases/nu_v1_plate27_notes_A.jpg`, plat image `nu_v1_plate27_inset_school_section_plat.jpg`). Column containing Blocks 44-37 is labelled **358** (ft E-W); N-S street widths "40 Ft."; original block depth in the row of Block 38 is 396 (right-margin labels "396", bottom row "462").
* **"F"** — "Sub. of Blks. 14, 15, 16, 28, 33, 34, 35, 38, 39, 40, 54, 57, 58, 59, 62, 63 & 64 in S.S. Add. Rec. May 4, 1835, in B. 6, p. 379 to 382. Copied from the books of Handy & Co." (`atlases/margin_notes_part1.png`). This is the subdivision that created lots 1-7 (Taylor front), 8-14 (De Koven north front), 15-17 (Jefferson front south of De Koven) and 18-21 (De Koven south front) of Block 38.
* **"G"** — "H. T. Weeks' re-sub. of the W. ½ of lot 13 and all of lot 14 in Blk. 38 … Rec. Jan. 29, 1874 … Ack. by Harvey T. Weeks, Jan. 15, 1874" — five lots 20.15 ft (N-S) × 83.4 ft (E-W) facing Jefferson (plate 28 labels "20.15", "83.4"). Post-dates the fire; in 1871 this ground held Frank Shult's corner saloon and the 20×40 dwellings on Musham's plan.
* **"H"** — "Sub. of lots 15, 16 & 17 Blk. 38 S.S. Add. … Rec. April 10, 1883" — the lots facing Jefferson south of De Koven (H lots 1-6; H lots 1 and 2 = 25 ft each on De Koven, 100.6 deep; lots 3-6 100 ft deep on Jefferson; 8.5-ft private alley east of them). **Confirms that the ground south of De Koven is still Block 38**, i.e. De Koven was cut through the original 396-ft block.
* **"I"** — "Sub. of Blk. 37 in S.S. Add." (lots 33-45 on Bunker) — Block 37 lies south of the "dividing line" alley.
* **Alley ordinance** (plate 27 table, `atlases/nu_v1_plate27_ordinance_table_fullres.jpg`): "Opening of alley on N. [¼] line Blks. 11, 14, 35 & 38, from Halsted st. to Clinton st. — width 15 — passed July 30, 1855 / Sept. 15, 1855 — No. 2027 — assessment confirmed Feb. 14, 1856." The fraction glyph is small (zoom in `ordinance_fraction_zoom.png`); ¼ of the original 396-ft block = 99 ft, which is where the alley is (99-100 ft south of the Taylor line), so I read it as ¼. A second entry opens the 15-ft alley "from Halsted st. to Canal st." on the "dividing line bet. Blks. 11, 14, 35, 38 & 59 and Blks. 12, 13, 36, 37 & 60" (the alley south of lots 18-21).
* **De Koven/Bunker location survey**: plate 27 inset "Plat showing location of DeKoven and Bunker streets by a survey made Nov. 4th and 12th, 1875" (`atlases/nu_v1_plate27_inset_dekoven_survey_1875.jpg`) — covers the blocks west of Jefferson only, but gives the depths of the adjoining blocks: north halves 100.64 / 100.83 / 99.55, south halves 100.61 / 100.83 / 99.14, alley 15, De Koven "60" (with "40" also marked at Halsted).

### 1.2 Dimensions of Block 38 used in the CSV
| item | value (ft) | source | resolution |
|---|---|---|---|
| Block width Jefferson E line → Clinton W line | 358.4 (358 on 1833 plat; 83.4 + 25 + 5×50 = 358.4 from sub-lot dims) | 1833 plat label; G-sub 83.4; "E ½ of lot 13" 25; lots 8-12 at 50 (1891 plate 4.03 px/ft; 1906 Sanborn 25-ft number spacing) | survey plat / atlas ±1.5 |
| Lot 14 (west lot) | 58.4 | 83.4 − 25 (G-sub = lot 14 + W½ 13) | plat |
| Lots 13, 12, 11, 10, 9, 8 | 50 each | 1891 plate 200 px = 50 ft; parcel vertices at 108.6, 158.4, 208.4, 308.3 | atlas + parcel ±1 |
| Lot 1 (west, Taylor) / lots 2-7 | 58.4 / 50 | 1891 plate 230 px / 200 px; parcel north-edge vertices at 58.6, 108.5, 158.0, 208.4, 308.3 | atlas + parcel |
| Depth of De Koven-front lots (south half) | **100.75** | G-sub 5 × 20.15; parcel east edge shows 99.8 | survey plat |
| Alley | **15** (opened 1855, ordinance) — Musham "Alley 15' wide" — the report gives Andreas plat 16, Sullivan testimony ~12 | ordinance / plan | plat |
| Depth of Taylor-front lots (north half) | ~100 (99.55-100.83 on adjoining blocks, 1875 survey; 1891 plate 400 px ≈ 101) | 1875 survey / atlas | ±1.5 |
| Block N-S (Taylor S line → De Koven N line) | 215.75 ≈ 100 + 15 + 100.75 | derived | ±2 |
| De Koven St width | **60** (1891 plate "60"; Musham "60 feet wide"; Sanborn 1906 "60'" at both ends; modern OSM centreline 29.4-31.8 ft from parcel edge) | | plat/atlas |
| Jefferson St | 40 (Musham "40 feet wide"; 1891 plate "40"; Sanborn 1906 "40'"); modern ≈ 74 | | |
| Clinton St | 40 (Sanborn 1906 "40'"); modern ≈ 75 | | |
| Taylor St | 60 (1891 plate, Sanborn 1906); modern ≈ 80 | | |
| South side of De Koven, west→east | orig. lots 15-17 (100 ft deep on Jefferson) / 8.5-ft private alley / H-lot 2 (25) / H-lot 1 (25) / lots 18, 19, 20, 21 (50 each) = 358.5 | 1891 plate labels "100", "8.5", "25", "25"; Sanborn 1906 "8.5" | plat |
| Depth of south-side De Koven lots | 100.6 (H lots 1-2 "100.6"); the 1875 survey gives 101.16-101.27 for the adjoining block | plat |

### 1.3 Modern anchor (Cook County parcel) and how every lat/long in the CSV was derived
* Source: Cook County GIS "Parcels 2021" (Socrata 77tz-riq7, GeoJSON, `parcels/cook_parcels_2021_block.geojson`), PIN **17-16-324-029** (Chicago Fire Academy, class EX). The polygon (22 vertices) measures 320.0 ft along De Koven and 194 ft N-S (79.2 + 15.0 + 99.8 on the east edge; 4 × 20 + 34.9 + 79.2 on the west edge).
* **Why the parcel is a good anchor**: its vertices sit on the old lot lines — east-edge segments 15.0 ft (the alley) and 99.8 ft (the De Koven-front lot depth, plat 100.75); west-edge vertices every 20.0 ft (the G-sub 20.15-ft lots); south-edge vertices at 65.3, 90.2, 140.0, 190.1, 290.0 ft from its SW corner, which are the plat lot lines 83.4, 108.4, 158.4, 208.4, 308.4 **each minus 18.3 ft**; north-edge vertices at 40.3, 90.2, 139.7, 190.1, 290.0 = plat 58.4, 108.4, 158.4, 208.4, 308.4 minus 18.3 (spread 0.4 ft). Hence the parcel's west edge is 18.3 ± 0.5 ft east of the 1871 Jefferson line (street widening), and its east edge is 358.4 − 18.3 − 320.0 = 20.1 ft west of the 1871 Clinton line. North: 79.2 ft remain of the ~100-ft north half (Taylor widened ~21 ft on this side). South edge: on the De Koven north line (De Koven unchanged; OSM centreline 30 ft south).
* **Origin O** = parcel SW corner (−87.6421042, 41.8690785) moved 18.3 ft along the parcel's south edge (bearing 268.95°): **O = 41.869078 N, −87.642172 W** (±2 ft). x-axis = parcel south-edge direction (bearing 88.95° = grid east; true north of the grid is 1.05° west of the grid's y-axis… i.e. grid north bears 358.95°); y-axis perpendicular. Flat-earth conversion at 41.8693 N (1° lat = 364 567 ft; 1° lon = 271 540 ft).
* Every row in `plan_coordinates.csv` is (x, y) in that frame plus lat/lon from `from_plan()`; the "source" and "resolution" columns say which dimension produced it. Rows in short:
  - Academy parcel corners — GIS polygon, ±2-3 ft absolute.
  - Block corners — plat dimensions above (±2 ft).
  - Lot west lines on De Koven (0, 58.4, 108.4, 158.4, 208.4, 258.4, 308.4) — plat, ±1 ft; alley lines y = 100.75/115.75 — plat.
  - O'Leary lot 133.4-158.4 × 0-100.75 — E½ lot 12 (Andreas affidavit) — plat ±1.5.
  - O'Leary barn 133.4-153.4 × 84.75-100.75 — **estimate**: 20 ft E-W × 16 ft N-S on the west side of the lot against the alley, passage on the east (Musham 1940 plan and text "along the east side of the lot and passing the barn was a passageway to the alley"; Andreas: barn's south line 8 ft north of Dalton's rear ≈ 78 + 8 = 86). If the barn was 16 ft E-W × 20 ft N-S (the Andreas plat as given in the report, 9-ft passage) use 133.4-149.4 × 80.75-100.75 — both variants are in `plan/musham_plan_digitized.csv`/§2.1. ±3 ft.
  - O'Leary cottages 137-153 × 2-38 — Andreas "thirty-six feet north and south, the front being nearly on the street building line"; Musham "each about … 16 wide"; Musham plan draws them 3.6-40 ft back and 3 ft in from the west line. ±3 ft.
  - Dalton house 158.4-178.4 × 38-78 — Andreas (on the west line of his lot; front 2 ft south of the O'Leary cottages' north line; 40 ft deep); width **not given** by any source (Musham draws ≈ 20 ft) → estimate. Dalton shed 12 × 20 at the alley on the west side (Andreas), 8-ft fence house→shed on x = 158.4.
  - South side: Block 38 south part NW corner (0, −60); lot lines at 100, 108.5, 133.5, 158.5, 183.5, 208.5, 233.5, 258.5 …; 134 = 183.5-208.5, 130 = 233.5-258.5 (plat + numbering, §5) ±2 ft.
  - Fire Academy footprint (Chicago Building Footprints, syp8-uezg, bldg 369839): front wing x 65.6-217.7, y 13.6-80.6; west wing x 32.3-65.3, y 75-188.6; rear wing x 101.6-127.5 to y 181.8-188.6 (±3 ft). OSM way 155559107 agrees within 5 ft.
* Cross-checks: OSM centrelines (`parcels/overpass_block.json`): Jefferson centreline 39.6 ft west of the parcel edge (modern ROW ≈ 74 ft = 40 + 18.3 + 15.7); Clinton centreline 38 ft east of the parcel (ROW ≈ 75); De Koven centreline 29.4-31.8 ft south of the parcel edge (60 ft ✓); Taylor centreline 44-46 ft north of the parcel (ROW ≈ 80-90).

### 1.4 Post-1909 numbering
Under the 1909 system (State St = 0; Clinton 540 W, Jefferson 600 W; 100 numbers per 660 ft) the E½ of lot 12 (153-178 ft east of the Jefferson centreline) computes to about **574-578 W. De Koven**; **558 W. De Koven** is the Fire Academy's address for the whole block (landmark file: "558 West DeKoven Street (then numbered as 137 DeKoven Street)"). Pre-1909 numbers on De Koven increase westward from the river (Block 59 east of Clinton 101-115; Block 38 121-141 north side, 122-148 south side), 2 per 25 ft.

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## 2. Buildings in 1871

### 2.1 Dimensions stated in sources (exact wording)
| source | wording | file |
|---|---|---|
| Andreas, *History of Chicago* II (1885) 713-14, statement of James E. Dalton (No. 135) | "O'Leary had two small cottages, one immediately behind the other, though practically attached. The two were thirty-six feet north and south, the front being nearly on the street building line. There was a space of about forty feet between the north end and the barn, used as a 'back yard.' Dalton's cottage set back from the street, leaving room for a contemplated front addition. It stood four feet above the ground, on cedar posts. The front of his cottage was two feet south on the north line of O'Leary's cottages, and his house was forty feet deep. The south line of O'Leary's barn was eight feet north of the rear of Dalton's house. His cottage was built on the west line of the lot. There were three west windows which looked on the O'Leary yard. A fence, eight feet high, ran from his house to his shed, at the rear of the lot, which was also on the west side. The shed was twelve by twenty feet in size." | `texts/historyofchicago02andr_djvu.txt` l.140633-140680; page image `texts/andreas02_leaf0786_s2.jpg` |
| Andreas II:708 | "The upper portion of the building had recently been filled with hay … High wooden fences ran from the barn to sheds on contiguous lots"; McDermott affidavit: "at No. 137 DeKoven Street, on the east half of Lot 12, in Block 38, School Section Addition"; "Dennis Sullivan, who happened to be sitting in front of his own house, nearly opposite the O'Leary place" | `texts/andreas02_leaf0780_s2.jpg` |
| Andreas II:709 (Board of Police & Fire report) | "the fire originated in a two-story barn in the rear of No. 137 DeKoven Street … first discovered by a drayman by the name of Daniel [Dennis] Sullivan, who saw it while sitting on the sidewalk on the south side of DeKoven Street, and nearly opposite O'Leary's premises"; Musham (foreman No. 6): "Laying his hose up the passageway on O'Leary's lot, running north from DeKoven Street"; affidavit of Dennis Sullivan: "he went a few lots east of O'Leary's on the opposite side of DeKoven Street, until about half-past nine o'clock, when he saw the fire" | `texts/andreas02_leaf0781_s2.jpg` |
| Andreas II:716 | Frank Shults (saloon, cor. De Koven & Jefferson): mother-in-law "looking out of the window in the second story of their house, saw the fire in O'Leary's barn" not later than 8:45; Joseph Puzner, 442 Clinton St, "three doors south of DeKoven" | `texts/andreas02_leaf0788_s2.jpg` |
| Musham, "The Great Chicago Fire", *Papers in Illinois History* 1940, pp. 94-95 | "two small frame cottages, each about 36 feet long by 16 wide, one of which fronted on the street, the other being but a few feet to the rear. At the rear end of the lot, which was 25 feet wide by 100 deep, was a story and a half barn, 20 by 16 feet in size, about 16 feet high and with a peaked roof. It was built of one inch planks and two-by-fours, the planking being set on end. Along the east side of the lot and passing the barn was a passageway to the alley which was 15 feet wide." "… lined with barns and sheds in one of which, 25 feet east of the O'Leary barn, was a small paint shop." (NB "each about 36 feet long" contradicts Andreas's 36 ft for both; a 36-ft E-W cottage cannot stand on a 25-ft lot.) | `texts/papersinillinois1940illi_djvu.txt` l.4160-4185 |
| Musham 1940 p. 98, plan "THE START OF THE FIRE" (scale bar 0-100 ft) | Jefferson "40 feet wide", De Koven "60 feet wide", "Alley 15' wide"; O'Leary barn "16'x20'" drawn 20 E-W × 18 N-S at the alley on the west side; sheds 12'x25', 12'x20'; "2 story barn 20'x20'" + "Ice House 12'x12'" (rear of 141); "2 story barn 20'x25'" (rear of 133); sheds "10'x25'" ×4 and "Paint Shop" north of the alley; Shult's saloon "2 stories 20'x60'"; No. 141 "Large frame house", 139 "Cottage Mrs. Annie Murray", 137 "Cottages Patrick O'Leary / Patrick McLaughlin", 135 "Cottage James Dalton", 133 "Cottage Morris Connovan / William Lee / Walter Forbes". Digitised at 4.12 px/ft in `plan/musham_plan_digitized.csv` (±2 ft). | `texts/musham_1940_page114.png`, `texts/musham_1940_p98_plan_4x.png`, `texts/musham_plan_grid.png` |
| Sheahan & Upton, *The Great Conflagration* (1871), Appendix pp. 423-428 (inquiry summaries) | Mrs McLaughlin: "she looked around the side of the house and saw O'Leary's barn was burning, and the rear part of Mr. Dalton's house was just igniting … The barn was about forty feet from the house"; Patrick O'Leary: "Both doors of the barn were open—the alley door and the one on the south side of the building. The latter was nailed back so that it could not be shut. On the right hand side of the barn, going north, there were some shavings and wood, and in a shed outside were some coal and more wood"; "Daniel Sullivan, of No. 134 DeKoven street … while on the opposite side of the street, at twenty or twenty-five minutes past nine o'clock, he saw fire in O'Leary's barn. He ran across the street as fast as he could—he has a wooden leg"; Mrs O'Leary: "Mr. Sullivan, drayman, who lives on the south side of DeKoven street" | `texts/greatconflagrati0000shea_djvu.txt` l.16600-16830 |
| Colbert & Chamberlin 1871 | no dimensions of the premises (OCR checked for Leary/Koven: only rhetorical mentions) | `texts/chicagogreatconf1871colb_djvu.txt` |
| Commission on Chicago Historical and Architectural Landmarks, *Site of the Origin of the Chicago Fire of 1871* (June 1971) | "The O'Leary property was a 25' by 100' lot on the north side of De Koven Street … two small shingled cottages, one close behind the other, and behind them, a barn … The 40' between the rear cottage and the barn was utilized as a back yard. The infamous barn was constructed of wood and was 16' by 20' and 14' high." | `texts/chicago_landmark_site_of_fire.txt` |

### 2.2 The two disagreements in the record
1. **Barn orientation.** As given in the report: Andreas's 1885 plat draws the barn 20 ft N-S × 16 ft E-W on the west side of the parcel with a 9-ft passage on the east; Musham 1940 draws 20 ft E-W × 16 ft N-S. I could not find that Andreas plat on the pages fetched (708, 709, 714, 716; the only plat on 714 is "West line of fire"), so I cannot check it, but the arithmetic is: 25-ft lot − 16-ft barn = 9-ft passage (Andreas version) vs 25 − 20 = 5 ft (Musham version). Musham's plan is explicitly labelled "16'x20'" yet drawn 20.6 ft wide × 18 ft deep; Andreas's text (8 ft between Dalton's rear at ≈78 and the barn's south wall) gives the barn's south wall at ≈86 ft, which fits a 16-ft-deep barn on the alley (84.75-100.75) better than a 20-ft-deep one (80.75-100.75), but the difference (4 ft) is inside the uncertainty of Dalton's "forty feet deep". Both variants are tabulated; the choice moves the barn's south wall by 4 ft and its east wall by 4 ft — small compared with the sight-line margins in §2.6, but it should be carried as a ±4 ft uncertainty.
2. **Alley width.** 1855 ordinance and the 1891 plate: 15 ft (plate labels the block-38 alley only "opened by ordinance"; the "15" is in the ordinance table and on the Bunker-side alley "15.5"/"15"); Musham 1940: 15; the modern parcel's east-edge vertex segment: 15.0 ft; 1875 survey of the adjoining blocks: 15; the report gives Andreas's plat 16 and Sullivan's testimony ~12 (Sheahan & Upton's summary of Sullivan is silent on it). I take 15 ft (recorded and surviving in the parcel geometry); a witness's "12 ft" is the kind of figure people give by eye.

### 2.3 Building heights — ranges and basis
| building | height range | basis |
|---|---|---|
| O'Leary barn | 14-16 ft to the ridge ("14' high" landmark file 1971, evidently from an 1871 source; "about 16 feet high and with a peaked roof … story and a half" Musham; "two-story barn" Board report 1871). Eaves therefore ≈ 9-11 ft, loft floor ≈ 8 ft. | text |
| O'Leary cottages (front McLaughlin / rear O'Leary) | **estimate from the Abbott stereograph** (`gcf_images/oleary_cottage_1871_abbott_stereograph_ichi-02741.jpg`, 8605×4420; measured on `stereo_cottage_front_grid.png`): the man on the walk at the foot of the steps is 540 px from hat-top to feet; taking him as 5.6-6.0 ft with hat → 90-96 px/ft. Door sill ≈ 210 px above the walk → **floor 2.0-2.5 ft above the walk**; wall top/eave at the near corner ≈ 860 px above the sill → **wall 9-9.5 ft**; the roof is seen at a grazing angle so the ridge cannot be measured directly; for a 16-ft-wide gable-front cottage of ordinary pitch (rise 3-5 ft) the **ridge is 12-14.5 ft above the floor, i.e. 14-17 ft above the walk**. The walk is a raised plank sidewalk on posts: visible post height ≈ 1.5-2.5 ft (150-230 px) → **walk 1.5-2.5 ft above the ground**, so eaves ≈ 13-14.5 ft and ridge ≈ 16-19 ft above the ground. Picket fence: pickets reach the man's shoulder → 4.5-5 ft. Orientation caveat: the photograph shows a gable end with the door at the left and a ~36-ft clapboard side with two chimneys receding to the right, a picket fence along that side and the plank walk in front of the fence; if the walk is the De Koven sidewalk the long side faced the street, which a 25-ft lot cannot accommodate for a 36-ft building — more likely the camera stood in a burnt-out neighbouring lot and the walk/fence run along the lot side; the height measurements do not depend on this. | photo, ±10-15 % |
| Dalton cottage (135) | one storey on cedar posts 4 ft above ground (Andreas). With typical 8-9 ft walls: **eaves 12-13.5 ft, ridge 15-19 ft above ground** (estimate; pitch unknown). Set back 38-40 ft; 40 ft deep; width unknown (Musham draws ~20). | text + estimate |
| 133 cottages (Forbes / Lee / Connovan) | 1½ storey per the Andreas plat (as given in the report) → **eaves 10-12 ft, ridge 17-22 ft** (estimate). Musham draws three cottages in a row on the lot (x 186-205, y 3.6-60.7); Andreas: Forbes "adjoining Dalton's on the east", Lee "two doors east of the O'Leary cottage" with "the blinds on the west window". | plan + estimate |
| 2-storey barn on 133 (rear) | "2 story barn 20'x25'" (Musham plan) → **18-24 ft to the ridge** (estimate; two-storey frame barn). Mrs O'Leary: "three barns—two besides her own—on fire at the same time". | plan + estimate |
| Dalton shed 12 × 20 (alley, west side) | one storey shed, **8-11 ft** (estimate). "Shed 12'x20'" on Musham's plan. Lee first "thought the flames were in James Dalton's shed, in the rear of No. 135". | text + estimate |
| Fences | Dalton's board fence house→shed on the O'Leary/Dalton line: **8 ft** (Andreas); "High wooden fences ran from the barn to sheds on contiguous lots" (Andreas 708) — take 6-8 ft; front picket fences 4-5 ft (stereograph); Mrs McLaughlin's testimony (per Bales) implies another fence from the front of Dalton's house. | text |
| Shult's saloon (corner) | 2 storeys (Musham; Andreas: fire seen from a second-storey window) → eaves ≈ 18-22 ft. | text |

### 2.4 Occupants — every 1869-72 directory entry found (exact OCR wording; `directories/directory_extracts.txt`, full texts in `directories/`)
*Edwards' 12th Annual Directory 1869-70* (`edwardsannualdir12186970chic_djvu.txt`): "Leary Patrick, lab. r. 137 DeKoven"; "Leary Patrick, sawyer, John Phillips, r. 130 DeKoven"; "White William, lab. r. 130 DeKoven"; "White Thomas, lab. r. 116 DeKoven"; "Sullivan Catherine, wid. Eugene, r. 134 DeKoven"; "Dalton James, builder, r. 135 DeKoven"; "Forbes Walter, carpenter, r. 133 DeKoven"; "Connell Mary, wid. Michael, r. 139 DeKoven"; "Patchin Clement, pat. medicine mkr. r. 138 DeKoven"; "Jones Morris, lab. … r. 136 DeKoven"; "Jones Richard, lab. r. 136 DeKoven"; "Underwood John A. r. 136 DeKoven"; "O'Neil Charles, shoemaker, r. 140 DeKoven"; "Scott Alexander, seaman, r. 140 DeKoven"; "Kotau Joseph, musician, r. 131 DeKoven"; "Biesch Joseph, carpenter, r. 128 DeKoven"; "Brumski Wenzel, shoemaker / Malone Martin, lab. / O'Donnell John, lab. / Reid John, printer / Singsheim Peter, lab. — r. 129 DeKoven"; "Grennock John, lab. r. 127 DeKoven"; "Dushek William, milkman, r. 153 DeKoven"; entries at 132 and 143 exist but the names are OCR-garbled. No McLaughlin Patrick at DeKoven; no Sullivan Daniel; no Regan/Rogan Dennis; "Cohn Louis, tobacco and cigars, 151 Clark" / "Cohn Louis, tailor, 292 Wells" (no DeKoven Cohn).
*Edwards' 14th Annual Directory 1871* (`edwardsannualdir141871chic_djvu.txt`): "McLaughlin Patrick, lab. r. 137 DeKoven"; "Field Nelson, framemkr. r. 137 DeKoven"; "Sullivan Daniel, teamster, Chase, Hanford & Co. r. 135 DeKoven"; "Sullivan John, teamster, Chase, Hanford & Co. r. 135 DeKoven"; "Sullivan Catherine, wid. Eugene, r. 134 DeKoven"; "White William, teamster, Chase, Hanford & Co. r. 130 DeKoven"; "White Thomas, lab. r. 116 DeKoven"; "Dalton James, carpenter, r. 135 DeKoven"; "Lee William, blksmith. r. 133 DeKoven"; "Canavan Morris, sailor, r. 133 Dekoven"; "Bettertil A. carriagemkr. r. 141 DeKoven"; "Vanek Franklin, lab. r. 141 DeKoven"; "Zachimsta William, plumber, r. 141 DeKoven"; "Nolten(?) Francis, r. 136 DeKoven"; "Scott Alexander, r. 140 DeKoven"; "Hunniger Frederick, butcher, r. 122 Dekoven"; "Busch V. / Chmadal Joseph, tailor / Kohr(?) Joseph / Rutbaugh Franklin, carpenter — r. 131 DeKoven"; "Kolbaba John, clk. / Novie Joseph, grocer — 125 DeKoven"; "Krenik Jan, saloon, 127 DeKoven"; "Duchet William, milkman, 153 DeKoven"; "TURNER HALL—106 and 108 DeKoven". **No O'Leary/Leary Patrick at 137 in 1871** (the O'Learys are absent from the 1871 volume); no Regan/Rogan Dennis under any spelling; "Cohn Louis, cigar mnfr … S. Park av.", "Cohn Louis (Kale & Cohn), r. 313 State", "Cohn Louis, clothier, r. 62 4th av." (none on DeKoven). Note: the Sullivans' "135" (north side, Dalton's number) vs. Catherine Sullivan's and the inquiry's "134" — a misprint or a boarding entry; every 1871 source puts Daniel Sullivan on the south side at 134.
*Edwards' Chicago Census Report and Statistical Review 1871* (`chicagocensusrep01edwa_djvu.txt`): "Dalton James, carpenter, r. 135 DeKoven, w 9 m 6 f …"; "Bettertil A. carriagemkr. r. 141 DeKoven"; "Burke James, lab. r. 130 DeKoven"; "Field Nelson, framemkr. r. 127 DeKoven"; "Amman Michael, tailor, r. 120 DeKoven"; "Corchran John, mason, r. 112 DeKoven"; "Foote Daniel, lab. / Frundel Frank, lab. / Frundel Thomas — 113 DeKoven"; no O'Leary, McLaughlin, Sullivan, White, Regan entries on DeKoven found.
1870 (13th) and 1872 (15th) Edwards directories: **not on archive.org** (searches `directories/ia_search_*.json`); HathiTrust unreachable → shortfall.

### 2.5 What the 1891 plate and 1906 Sanborn show on lots 18E (134) and 19E (130), and what they cannot say
* 1891 (Greeley-Carlson pl. 28, `atlases/grid_blk37_north.png`, archival px → ft at 4.03 px/ft E-W, ≈3.9 N-S): 18E (134): a 2-storey frame building ("2S", yellow) spanning the half-lot, front ≈ 11 ft back from the street line, ≈ 18 ft deep (x 185-208, y −71 to −89) with another 2-storey frame ("2B") east of it; 19E (130): a 2-storey **brick** ("2B", pink) x ≈ 232-251, front ≈ 8.5 ft back, ≈ 60 ft deep (y −68 to −130). Lot 18W (136): "2B" frame; 19W (132): "2B" frame.
* 1906 (Sanborn vol. 1 sheet 110, `sanborn/s110_blk37_north_half.png`): 134: "2 D" frame dwelling ≈ 17 ft wide, front set back ≈ 13 ft, ≈ 43 ft deep, small "1" frame outbuilding at the rear; 136: "2BB D, BR. 1st" (2-storey frame over brick first storey, at the street line); 132 and 130: "3 F" brick flats, 130's at the street line and ≈ 60 % of the lot depth; 128: "2B D" frame; 126: "3B F" brick; 124: "2BB D" frame; 122: "2B S in B'st" frame store; 140/138: "4B F" brick flats; 148 corner: "Iron Yard". Street: "DEKOVEN 60'"; private alley "8.5"; De Koven-front lots 100.6 deep.
* **Limits**: both maps post-date the fire by 20-35 years and show rebuilt property; the 1871 buildings on 134 and 130 (both frame cottages — Catherine Sullivan: "Her house caught fire several times, and citizens threw pailsful of water on it") are not recorded on any map I obtained. The maps fix only the lot lines, the 25-ft frontages and the numbering. They cannot say whether the lot west of Sullivan's was vacant in 1871. Directory evidence on that: 136 had residents in 1869-70 (Jones, Underwood) and 1871 (Nolten); 138 has one 1869-70 resident (Patchin) and none in 1871; 132 has a garbled 1869-70 entry and none in 1871. Bales (2002, p. 137, Google-Books snippet) reads Andreas's "vacant lot" west of Sullivan's home as "the middle half-lot"; Bales also states (p. 195) that "in 1871 William White owned two contiguous parcels of land on DeKoven Street, a west [parcel …]" and (p. 137) "the east half of lot 19", so White's "head of his lot" could be anywhere in x 208.5-258.5.

### 2.6 Sight-line geometry (straight lines, plan view; `plan/draw_plan.py` output)
Candidate seats (sidewalk, y ≈ −62 to −66): S1 front of 134 (x 196); S2 front of 130 (x 246); S3/S4 = W/E corners of White's E½ lot 19 at the street line (233.5 / 258.5). Targets: barn SW (133.4, 84.75), SE (153.4, 84.75), NE (153.4, 100.75). x where the line crosses Dalton's front (y = 38) and rear (y = 78); Dalton house assumed x 158.4-178.4:
| seat | to barn SW: x@38 / x@78 / dist | to barn SE | to barn NE |
|---|---|---|---|
| S1 (196, −64) | 153.1 / 136.2 / 161 ft — clears Dalton, crosses O'Leary rear cottage (x 137-153, y 23-40) at its NE corner | 166.8 / 155.3 / 155 — through Dalton's west part | 169.6 / 159.3 / 170 — through Dalton |
| S2 (246, −64) | 168.8 / 138.5 / 187 — through Dalton | 182.5 / 157.6 / 175 — Dalton's east edge, then over the 8-ft fence line | 188.7 / 166.2 / 189 — through 133 cottages then Dalton |
| S3 (233.5, −62) | 165.3 / 138.0 / 178 | 178.9 / 157.1 / 167 | 184.3 / 164.6 / 181 |
| S4 (258.5, −62) | 173.3 / 139.2 / 193 | 186.9 / 158.2 / 181 | 193.9 / 168.1 / 194 |
Vertical check (estimate): eye of a seated man on a walk 1-2 ft above grade ≈ 4.5-5.5 ft; barn ridge 14-16 ft; at Dalton's front wall (≈ 100-110 ft from the seat, 45-60 ft short of the barn) the line to the ridge is ≈ 11-12.5 ft above grade — below Dalton's estimated eaves (12-13.5 ft). So from S2-S4 the barn itself was hidden and only flame above the roof ("burst through the roof … a billow of flame", Musham) could be seen; from S1 the west half of the barn is seen over the O'Leary yard/rear cottage. The 193-ft figure attributed to Bales (run from White's to the barn) matches S4→barn SW/NE (193-194 ft straight line).

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## 3. De Koven Street width and sidewalks
* Width **60 ft**: 1891 plate "60" at both ends of the block; Musham plan "De Koven Street 60 feet wide"; Sanborn 1906 "60'" at Jefferson and Clinton; modern OSM centreline 29.4-31.8 ft from the parcel edge (unchanged). (The 1875 survey plat also carries a "40" beside "60" at Halsted, i.e. the street was dedicated at 40 and widened to 60 before 1871 at least east of Jefferson — not verified for this block.)
* **Sidewalk widths: no source found gives them.** Musham: "The sidewalks were of wood and in many places built on posts"; the Board report: "sitting on the sidewalk on the south side"; the stereograph shows a plank walk ≈ 5-6 ft wide on posts (estimate from the plank count/perspective) in front of the O'Leary cottage. Chicago's 1871 sidewalk ordinance widths were not retrieved.

## 4. Why 137 = E½ lot 12 (the "E ½ of lot 13" reading and the numbering)
1. Direct statement: McDermott affidavit (Andreas II:708) "No. 137 DeKoven Street, on the east half of Lot 12, in Block 38".
2. The 1891 plate labels the 25-ft strip east of the G-sub "E ½ of lot 13" (`atlases/grid_blk38_south_dekoven.png`) and puts house numbers at one per 50-ft lot: 141 on that strip (x 83.4-108.4), 137 in lot 12, 133 in lot 11, 129, 125, 121 in lots 10, 9, 8. Sanborn 1906 shows every 25-ft half-lot numbered: 141, 139, 137, 135, 133, 131, 129, 127, 125, 123, 121 — eleven numbers on 11 × 25 = 275 ft = 358.4 − 83.4. Hence 141 = E½ 13, 139 = W½ 12, 137 = E½ 12, 135 = W½ 11 (Dalton, "next to O'Leary's on the east"), 133 = E½ 11 (Lee "two doors east"). The same rule on the south side (Sanborn 1906: 140, 138, 136, 134, 132, 130 … each 25 ft; 1891 plate: 140 on H-lot 2, 136 on lot 18, 132 on lot 19, 128/126 on lot 20, 122 on lot 21) gives 134 = E½ 18 and 130 = E½ 19, which is exactly Bales's tract-book finding for White (E½ lot 19).
3. Musham's plan, calibrated on its own scale bar with the west face of Shult's saloon as the Jefferson line, puts the "137" lot lines at 133 and 158 ft — the E½ of lot 12 to within 1 ft.

## 5. Environmental conditions (wind, humidity, temperature, rain)
* Signal Service, Chicago office (181 W. Washington; records lost in the fire; quoted by Musham 1940 pp. 95-96, 110, 172 from "Musham, Notes on the Weather at the Time of the Chicago Fire"): Sunday 8 Oct: 7:00 a.m. 51 °F, wind SW 19 mph ("a gentle breeze"), relative humidity 62 %, clear; 2:00 p.m. (unofficial) 85 °F, SW 35 mph "a high breeze"; 4:00 p.m. official 79 °F, 22 mph, "still clear and bright"; sunset 5:30 p.m. "leaving a flaming red sky, and the wind died down to a gentle breeze"; "At 9:00 p.m. the same gentle breeze was blowing from the southwest" (Musham citing Sheahan & Upton p. 160; Andreas II:715); "Just before midnight Sergeant Kaufman … read the anemometer on the roof and found that the wind was registering a speed of sixty miles per hour. This velocity is undoubtedly much too high." Musham's regional review (p. 171-72): "There were no high winds blowing; in only a few instances did the wind reach thirty miles an hour … The early hours of the night were very quiet." Reduced barometer Chicago 8 Oct: 7:00 a.m. 30.06, 4:00 p.m. 29.89, 11:00 p.m. 29.94 in; 9 Oct no observations (office destroyed). Forecast issued 7:35 a.m. 8 Oct: "The barometer will probably fall, with increasing southerly winds, and rising temperatures, followed by cloudy or threatening weather during the night." Witnesses: "a high wind" (Rogan), "The wind was very high, and the fire spread very rapidly" (P. O'Leary), "a severe breeze sprang up" about when the fire reached Taylor St (Musham, foreman No. 6).
* NWS Chicago 150th-anniversary page (`texts/nws_lot_1871fire.txt`; maps `astronomy/nws_*.png`): 7 Jul-8 Oct precipitation 3.55 in (≈ 8 in below normal, 2nd driest on record as of 2021); September 0.74 in on 3 days (15, 16, 28); no precipitation 29 Sep-8 Oct; highs mostly 70s-80s, dew points 30-50 °F, winds gusting 15-25 mph most days; 8 Oct highs low-mid 80s, RH 35-40 % afternoon/evening (Aurora observer), SW winds peaking ≈ 35-45 mph (observer estimates, "including within the city of Chicago"); 9 Oct highs upper 70s, gusts 35-45, RH ≈ 40 %, cold front late afternoon/evening, 0.10 in at Evanston; 10 Oct highs < 50 °F, RH ≈ 60 % by 7 a.m., winds W and light.
* Rainfall deficit per Musham p. 88 (citing Andreas II:703): "From July 3, when 1 50/100 inches of rain fell, to October 9, there was only 1 40/100 inches: August 3, 29/100; August 28, 54/100; August 30, 1/100; September 14, 36/100; September 15, 5/100; September 28, 11/100." Landmark file: "2-¾" of rain between July 3rd and October 8th, compared to an average rainfall of 8-¾"". (These totals disagree with the NWS 3.55 in; different station/records.)
* Light: sunset 5:30 p.m. LMT, end of astronomical twilight 7:02, moonset 3:03 p.m., moonrise 12:42 a.m.

## 6. The Saturday-night (Lull & Holmes) fire, 7-8 Oct
Musham pp. 89-90: "Between 10:00 and 11:00 p.m. on Saturday, October 7, a fire was discovered in the boiler room of Lull and Holmes's planing mill at 209 Canal Street. The mill, a two story brick building 60 by 100 feet in size, stood on the west side of the street between Jackson and Van Buren in a neighborhood known to insurance men as the 'Red Flash.' An alarm was turned in on Box 248 … A fourteen mile breeze was blowing from the south … The wind shifted to the southwest, blowing strongly. Within twenty minutes the blocks to the north and northeast were ablaze." Musham's map "The Saturday Night Fire" shows the burned area between W. Monroe/Adams and Van Buren, Canal and the river. greatchicagofire.org (`texts/gcf_landmarks_saturday_night_fire.html`): ignited "around 10 p.m."; "well into Sunday afternoon before this fire was extinguished, by which time four square blocks and close to a million dollars in property had gone up in smoke"; ten blocks north of De Koven. Landmark file: "four square blocks of cottages … Eight blocks from the mill fire was located the house and barn of the O'Leary family." Consequence (Musham/Andreas): No. 6 "Little Giant" and the other West Side companies exhausted; hose and engines damaged.

## 7. The site since 1871
* Landmark file (1971): O'Leary bought the lot in 1864 from Cyrus Clark for $500 and sold 8 Dec 1879; 1937 plaque (now "on the first floor of the Academy, near the spot where the great fire is said to have begun"); 1954 sale to the Chicago Land Clearance Commission ($6,500); 1955 the house then on the lot burned as a test blaze; **Chicago Fire Academy dedicated 15 May 1961**; landmark designated 1971; sculpture "Tongues of Flame" (a.k.a. Pillar of Fire) by Egon Weiner "on a paved plaza outside the building, at the northeast corner of the intersection of West DeKoven and South Jefferson Streets" (greatchicagofire.org: "just to the west of the entrance at Jefferson and DeKoven"). Relative to the 1871 plan the sculpture is therefore near x ≈ 20-60, y ≈ 0-15, i.e. on Shult's saloon/G-sub ground, 90-120 ft WSW of the barn site; the barn site itself (x 133-153, y 85-101) lies in the yard just north of the Academy's front wing (rear wall y ≈ 80.6), the cottages' site inside the front wing.
* No archaeological investigation of the site was found in any source consulted (landmark file, GCF site, Musham, NWS); the 1961 construction and the 1971 designation report contain no survey of the O'Leary lot.
* Overpass queries for a memorial node failed repeatedly (proxy resets); coordinates for the sculpture are therefore inferred from the texts only.

## 8. Published diagrams and images obtained (all in `SOURCES.md` with URLs)
* greatchicagofire.org / Chicago History Museum tile pyramids stitched at full resolution: `gcf_images/oleary_cottage_1871_abbott_stereograph_ichi-02741.jpg` (8605×4420; J. H. Abbott stereograph "Beginning of Fire"), `cause_of_the_great_chicago_fire_kellogg_bulkeley_ichi-34703.jpg` (6456×5052; 1872 lithograph), `lamp_found_in_olearys_barn_andreas_ichi-51076.jpg` (3765×4199), `origin_of_the_great_chicago_fire_crosby_1871_ichi-02945.jpg` (6266×4800; Crosby 1871) + `_2000px` copies; item pages view-item-665/255/269/669.html.
* Musham 1940 plan p. 98 (`texts/musham_1940_page114.png`, 4× render) and photo "O'Leary Premises After the Fire" p. 181 (`texts/musham_1940_page181.png`); Andreas II pp. 708, 709, 714 ("West line of fire" plat), 716 page images (`texts/andreas02_leaf078*.jpg`); Andreas engraving "O'Leary's barn" (p. 708).
* Greeley-Carlson 1891-92 vol. 1 plates 27-28 (Northwestern IIIF, archival 10367×13018; crops in `atlases/`); Sanborn 1906 vol. 1 sheet 110 full-res (`sanborn/v01NW_1906_sheet110_full.jpg`, 5834×7205) and sheets 108-109; LOC index sheets.
* Bales's figure (1997/2002): **not obtained** (JSTOR/NIU/archive.org restricted); the 1871 Tribune/Harper's sketches were not examined here.

## 9. Shortfalls (what could not be found or reached)
* Bales 1997 (*Illinois Historical Journal*) text and 2002 book (archive.org restricted; NIU Cloudflare; JSTOR bot wall) — only Google-Books snippets.
* The Andreas premises plat cited in the report (barn 16 × 20 N-S, 9-ft passage, 16-ft alley): not on pp. 708, 709, 714, 716; remaining pages 710-713, 715 not fetched (time limit).
* Edwards' 13th (1870) and 15th (1872) directories: not on archive.org; HathiTrust blocked.
* Original Signal Service forms (NCEI), docs.lib.noaa.gov daily maps (502); only Musham's transcriptions and the NWS 2021 page.
* HathiTrust, Chicago Collections, images.chicagohistory.org, web.archive.org: blocked (Cloudflare / proxy).
* Robinson 1886 and Rascher atlases, Ruger 1868 view: not downloaded (LOC 520/not located).
* Overpass memorial query (sculpture coordinates): connection resets.
* Sidewalk widths: no source.