# N05_E18 Great Lakes pilot: 1880–2020 population and geography crosswalk **Run date:** 2026-08-07 (America/Chicago) **Sector:** `N05_E18` **Canonical geometry:** 24 latitude bands × 24 longitude bands = 576 sectors; latitude 37.5°–45.0° N and longitude 270°–285° E (75°–90° W). **Pilot position:** Great Lakes nine-sector octagon centered on the N05_E18 working anchor at Merrillville, Indiana. **Time bands:** 1800–1950 historical transition; 2000–present modern baseline. **Status:** bounded research result; no sector score or `provisional_quadrant` assigned. ## Scope and selection The preceding N05_E18 note identified a specific unresolved path: retrieve an official machine-readable 2020 population/geography file that can be crosswalked to the fixed cell, and locate a historical census table for Lake County. This run completes that narrow crosswalk without treating place, county-subdivision, county, and fixed-cell populations as interchangeable. The modern source is the U.S. Census Bureau’s downloadable 2020 Census P.L. 94-171 Indiana file. The historical source is the Internet Archive scan of the 1880 Census compendium. Both are population-count sources, but their geographic definitions, enumeration methods, and spatial footprints require explicit separation. ## Search envelope - **Fixed cell:** `N05_E18`, 37.5°–45.0° N and 75°–90° W. - **Modern named geographies:** Merrillville town; Calumet, Hobart, and Ross townships; Lake County, Indiana. - **Historical administrative unit:** Lake County, Indiana, as listed in the 1880 aggregate county table. - **Variables:** total resident population; geography identifiers; land and water area metadata where transmitted in the geography file. - **Neighbor/exchange context:** the modern county-subdivision records are administrative anchors around the Merrillville/Gary/Calumet corridor, not a complete population surface for the 24 × 24 cell. ## Raw observations ### A. 2020 Census P.L. 94-171 downloadable file **Observation:** The Census Bureau’s Indiana download contains `in000012020.pl`, the segment-1 population file, and `ingeo2020.pl`, the geography file. Matching the geography records’ `LOGRECNO` to the population records’ `LOGRECNO` yields the following P.L. 94-171 total-population values. The values are retained as reported counts; no interpolation or area weighting was performed. | Geography | Census identifier | `LOGRECNO` | P.L. 94-171 total population | Source footprint / relation to N05_E18 | |---|---|---:|---:|---| | Merrillville town | `1600000US1848528` | `0009193` | 36,444 | Place-level working anchor; inside the fixed cell | | Calumet township, Lake County | `0600000US1808909820` | `0009537` | 91,970 | County subdivision; inside the fixed cell, not equivalent to the place | | Hobart township, Lake County | `0600000US1808934132` | `0000606` | 40,652 | County subdivision; inside the fixed cell, not equivalent to the place | | Ross township, Lake County | `0600000US1808966096` | `0000608` | 48,529 | County subdivision; inside the fixed cell, not equivalent to the place | | Lake County | `0500000US18089` | `0000046` | 498,700 | County-level anchor; extends beyond the fixed cell and must not be used as the cell total | **Source record:** U.S. Census Bureau, *2020 Census Redistricting Data (P.L. 94-171) Summary File*, Indiana, downloadable item `in2020.pl.zip`, published 2021-08-12. The relevant files are `in000012020.pl` and `ingeo2020.pl`. **Source URLs:** - Directory: - Download: - 2020 Gazetteer reference: - Census API documentation/catalog: ```yaml sector_id: N05_E18 period_id: 2000-present variable: population_settlement_profile subvariable: 2020_decennial_total_population value_type: enumerated_count unit: persons date_start: "2020-04-01" date_end: "2020-04-01" geographic_scope: "Named Census place, county subdivisions, and county; footprints are not equivalent to the fixed 24 x 24 cell" comparability: related_not_equivalent source_tier: A source: repository: U.S. Census Bureau identifier: "2020 P.L. 94-171 Indiana in2020.pl.zip" files: ["in000012020.pl", "ingeo2020.pl"] page_or_image: "Not paginated; LOGRECNO-linked fixed/pipe-delimited records" title: "2020 Census Redistricting Data (P.L. 94-171) Summary File" creator: "U.S. Census Bureau" publication_date: "2021-08-12" url: https://www2.census.gov/programs-surveys/decennial/2020/data/01-Redistricting_File--PL_94-171/Indiana/in2020.pl.zip extraction_method: "Downloaded file; matched LOGRECNO in geography and segment-1 population files" confidence: high missingness: geographic_match_uncertain notes: "No cell-wide total was derived; county and subdivision boundaries require a separate fixed-cell area crosswalk." ``` ### B. 2020 Census geography metadata **Observation:** The geography file identifies Merrillville as a place with internal point `41.4726873, -87.3180704`, Calumet township with internal point `41.5782998, -87.3531090`, Hobart township with internal point `41.5458565, -87.2642553`, and Ross township with internal point `41.4789410, -87.3066829`. These points fall within the N05_E18 latitude/longitude bounds. The geography records also transmit land and water area fields, but those fields are not used here to infer population density or cell coverage. The file identifies Lake County’s internal point as `41.5322734, -87.3899671`; the county’s full footprint is larger than the fixed N05_E18 cell. The county total is therefore contextual, not a substitute for the cell total. ```yaml sector_id: N05_E18 period_id: 2000-present variable: geography_crosswalk subvariable: named_place_and_county_subdivision_internal_points value_type: coordinate_observation geographic_scope: "2020 Census geographies in and around Merrillville/Gary/Calumet corridor" comparability: related_not_equivalent source_tier: A source: repository: U.S. Census Bureau identifier: "ingeo2020.pl" file: "ingeo2020.pl" page_or_image: "LOGRECNO records for Merrillville, Calumet township, Hobart township, Ross township, and Lake County" title: "2020 Census P.L. 94-171 geography file" creator: "U.S. Census Bureau" publication_date: "2021-08-12" url: https://www2.census.gov/programs-surveys/decennial/2020/data/01-Redistricting_File--PL_94-171/Indiana/in2020.pl.zip extraction_method: "Parsed geography records and compared internal points with fixed cell bounds" confidence: high missingness: geographic_match_uncertain notes: "Internal points establish an anchor relationship, not the fraction of each polygon inside the fixed cell." ``` ### C. Historical Lake County population table, 1860–1880 **Observation:** The 1880 Census compendium’s Indiana aggregate county table reports Lake County’s population as **15,091 in 1880**, **12,339 in 1870**, and **9,145 in 1860**. The table is printed on p. 26 of the volume and appears as PDF page 108 in the Internet Archive scan. This is a county-level historical count, not a Merrillville or fixed-cell count. **Source record:** United States Census Office, *Compendium of the Tenth Census (June 1, 1880)*, compiled by Francis Amasa Walker and Charles W. Seaton, published 1883, Table XVIII, “Aggregate population by counties—Indiana—Continued,” printed p. 26 / Internet Archive PDF p. 108. The page scan was inspected after OCR location; the OCR was not treated as the sole authority. **Source URLs:** - Item: - PDF: - OCR derivative: - Metadata: ```yaml sector_id: N05_E18 period_id: 1800-1950 variable: population_settlement_profile subvariable: lake_county_aggregate_population value: 15091 unit: persons date_start: "1880-06-01" date_end: "1880-06-01" geographic_scope: "Lake County, Indiana, as enumerated in the 1880 county table; not the fixed cell" comparability: related_not_equivalent source_tier: A source: repository: Internet Archive identifier: cu31924085506123 file: cu31924085506123.pdf page_or_image: "PDF p. 108; printed p. 26; Table XVIII" title: "Compendium of the Tenth Census (June 1, 1880)" creator: "United States. Census Office, Tenth Census; Francis Amasa Walker; Charles W. Seaton" publication_date: "1883" url: https://archive.org/details/cu31924085506123 extraction_method: "OCR used as locator; table page checked against the scanned page" confidence: medium missingness: geographic_match_uncertain notes: "The table supplies historical county totals; modern county/place/subdivision definitions and enumeration conditions are not assumed identical." ``` ### D. Existing anchor consistency check The 2020 P.L. 94-171 place record reports Merrillville at 36,444 persons, matching the 2020 estimates-base value already recorded in the project’s prior QuickFacts note. This is a source-consistency check for the named place anchor only. It does not validate the 2024 estimate, the full county total as a cell total, or the legacy sector narrative. ## Source interpretation The modern machine-readable file establishes a reproducible population/geography bridge for the N05_E18 working area: the Merrillville anchor is a 2020 Census place with 36,444 residents, and nearby Lake County subdivisions have separately reported totals. The records show why a sector study must preserve geography types rather than add overlapping or differently bounded units. Lake County’s 498,700 residents cannot be substituted for N05_E18’s population, and the three township totals cannot be added to Merrillville without double-counting or boundary analysis. The historical table adds a dated county-level population sequence: Lake County increased from 9,145 in 1860 to 12,339 in 1870 and 15,091 in 1880. That sequence is compatible with the transport and settlement transition documented in existing N05_E18 notes, but compatibility is not a causal finding. The historical county geography and the modern county/place/subdivision geographies are related administrative anchors, not directly equivalent cell measurements. ## Derived profile (not a quadrant) ### Derivation D1 — historical county growth arithmetic Using the reported Lake County totals without interpolation: - 1860 → 1870: `12,339 − 9,145 = 3,194` persons, approximately **34.9%** growth relative to 1860. - 1870 → 1880: `15,091 − 12,339 = 2,752` persons, approximately **22.3%** growth relative to 1870. - 1860 → 1880: `15,091 − 9,145 = 5,946` persons, approximately **65.0%** growth relative to 1860. These are arithmetic transformations of county totals. They are not cell-wide growth rates and do not establish that rail, waterworks, industry, or any single institution caused the change. ### Derivation D2 — modern geography crosswalk status - Merrillville, Calumet township, Hobart township, and Ross township have internal points inside the fixed N05_E18 bounds. - Lake County’s internal point is inside the cell, but the county footprint extends beyond it. - A defensible N05_E18 population total still requires polygon intersection with the fixed 24 × 24 cell and a documented treatment of partial geographies. - No population density, area-weighted estimate, township sum, or fixed-cell total was calculated in this run. ## Model classification ```yaml provisional_quadrant: unresolved classification_status: model_output_not_assigned reason: "The modern population observations are authoritative but are reported for named geographies with partial or nested footprints; the historical series is county-level and not directly comparable to the fixed cell. The pilot still lacks a frozen formula and complete cell-level raw-observation table." ``` `provisional_quadrant` remains a model output and is not an archival fact. ## Variable crosswalk | Modern measure | Historical measure | Status | |---|---|---| | 2020 Census Merrillville place total | 1880 Lake County total | Related but not equivalent; place versus county | | 2020 Lake County total | 1880 Lake County total | Potentially related after boundary and enumeration-method review; not accepted as directly comparable in this run | | 2020 county-subdivision totals | Historical county total | Related but not equivalent; subdivision boundaries and historical minor civil divisions require crosswalk | | Fixed-cell population | Any named geography above | Not yet derived; requires polygon intersection and documented allocation rule | | 2020 internal-point coordinates | Historical county table | Geographic anchor only; no historical point geometry supplied by the table | ## Confidence and missingness ### Confidence dimensions - **Source authority:** high for the Census P.L. 94-171 file and the official 1880 Census compendium. - **Geographic fit:** high for the named modern internal points falling within N05_E18; medium-to-low for using their totals as cell totals. - **Temporal fit:** high for the 2020 enumeration and 1860–1880 historical table dates. - **Measurement quality:** high for reported population counts; the historical table’s boundary and enumeration-method comparability remains unresolved. - **Extraction quality:** high for the modern file parsing; medium-high for the historical table because OCR was used for location and the scanned page was checked. - **Independent corroboration:** medium for the Merrillville 2020 count because it matches the prior QuickFacts estimates-base anchor; medium for historical context because prior local-history notes describe related settlement/transport change without reproducing this table. - **Comparability:** low-to-medium across historical county, modern county, modern subdivisions, and modern place. - **Known bias or limitation:** Census definitions, privacy-protected modern tabulation, county-boundary history, place incorporation, and enumeration practices can change the meaning of apparent population differences. **Summary confidence:** high for the bounded reported counts; medium for the anchor geography; unresolved for fixed-cell population inference. ### Missingness codes - `geographic_match_uncertain`: historical Lake County and modern named geographies are not the fixed N05_E18 polygon. - `historical_measure_not_available`: no 1850–1910 Merrillville-equivalent or fixed-cell population series was extracted in this run. - `period_match_uncertain`: 1860–1880 county counts are not a modern annual or place-level series. - `searched_no_result`: no accepted polygon-intersection result or historical boundary crosswalk was completed. - `not_applicable`: no missing population value was replaced with zero. Archival silence and absent fixed-cell allocation are not zero population. ## Falsification and alternative explanations The historical growth sequence could reflect migration, land speculation, agricultural settlement, railroad access, county-boundary or enumeration changes, and regional market integration. A transport-centered explanation must be tested against neighboring Great Lakes sectors using identical geographic and historical definitions. The modern administrative anchors may also overrepresent settled corridors relative to water, industrial, and low-density portions of the fixed cell. ## Next search path 1. Obtain 1850, 1860, 1870, 1880, 1900, and 1910 county and minor-civil-division tables with boundary notes, then construct a historical geography crosswalk rather than assuming modern township equivalence. 2. Acquire Census polygon files for 2020 places, county subdivisions, and the fixed N05_E18 rectangle; calculate only explicitly documented partial-area or dasymetric allocations. 3. Extend the modern population baseline with a gridded product whose cell resolution and version are recorded, keeping it separate from administrative counts. 4. Continue the 1950–2000 industrial-employment and energy bridge; do not infer employment from population totals. 5. Preserve `provisional_quadrant: unresolved` until the pilot’s cell-level raw-observation table, missingness handling, formula version, and matched-sector checks are complete. ## Provenance register 1. U.S. Census Bureau, *2020 Census Redistricting Data (P.L. 94-171) Summary File*, Indiana, `in2020.pl.zip`, files `in000012020.pl` and `ingeo2020.pl`, published 2021-08-12. 2. U.S. Census Bureau, *2020 Census Gazetteer Files* reference page. 3. United States Census Office, *Compendium of the Tenth Census (June 1, 1880)*, Table XVIII, Indiana, printed p. 26 / PDF p. 108, published 1883. Internet Archive item `cu31924085506123`. 4. U.S. Census Bureau, *QuickFacts: Merrillville town, Indiana*, V2024 display, retrieved 2026-08-07, used only as the prior anchor-consistency comparison. 5. Related project record: `2026-08-07-N05_E18-1850-1907-transport-waterworks-and-2024-population-anchor.md`. 6. Project method and fixed-grid rules: `08-research-sop.md`. ## Record limits This note adds a documented 1880 Lake County population sequence and a reproducible 2020 Census geography/population crosswalk for the N05_E18 working area. It does not calculate a fixed-cell population, complete the Great Lakes pilot, modify the legacy sector JSON, assign a score, assign a quadrant, or establish causal validity for the Macro-Culture thesis. No private data or secrets are included.