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Credits

Nothing here is original data. The index is public records, put side by side. These are the records, the references the method rests on, the software it runs on, and the people whose work set it going.

The idea

Louis Joyner, Architect, Columbus, Indiana, who inspired the idea: that the question of how a town of fifty thousand came to hold so much recognised architecture deserves a fair, public answer, measured against every other city.

Landmark Columbus Foundation, whose site inspired the look of this one: Futura, slate, one blue and one red. Credit to Jamie Goldsborough, the foundation's creative director, for that design.

Jonathan Nesci, designer, Columbus, Indiana, who helped refine the idea and the style, and whose collaborative practice, w/, work made with the region's makers, is the model for how this index should be built: with others.

Build Fractal, which built it. The American Institute of Architects' 1991 ranking of U.S. cities by architecture, which named Columbus sixth and was never repeated, is the list this index was made to replace with something reproducible.

Data

National Register of Historic Places
National Park Service. The listed-properties spreadsheet is the roster: every listing, its reference number, category, level of significance and areas of significance. The National Historic Landmarks list is the same service's. Public domain.
NRHP map service
National Park Service. A coordinate for each listing and, for districts, the count of contributing buildings. The coordinate is what places a listing inside a city. Public domain.
NPGallery
National Park Service. The nomination documents themselves: the forms and narratives that name a property's style, period and architect. The index archives each one and reads the text. Public domain.
TIGER/Line and the Gazetteer
U.S. Census Bureau. The legal boundary of every place, and its land area in square miles. Public domain.
American Community Survey
U.S. Census Bureau. Population (table B01003) and housing units (B25001), 5-year estimates, one vintage for every place. The Bureau's batch geocoder fills coordinate gaps. Public domain.
Wikidata and Wikipedia
Wikimedia Foundation and volunteers. Style, architect and build year where a volunteer has recorded them, and article text read for listings whose nomination names no style. Wikidata is CC0; Wikipedia text is CC BY-SA and is read, not republished.
Register Atlas
Open data at registeratlas.com, CC0. Build year, style and architect, cross-checked against the above.
Map tiles
OpenFreeMap, from OpenMapTiles and © OpenStreetMap contributors (ODbL).

Method references

Size classes
The Census Bureau's standard size-of-place classes, so cities compete with cities of their own size.
Style vocabulary
National Register Bulletin 16A, How to Complete the National Register Registration Form (National Park Service, 1997), whose architectural classification is the top of the tree, and Virginia Savage McAlester, A Field Guide to American Houses (second edition, 2013), for the styles, variants and periods beneath it.
Adjusted rate
R. J. Marshall, "Mapping disease and mortality rates using empirical Bayes estimators," Applied Statistics 40 (1991): the Poisson-gamma shrinkage that keeps a town with three listings from topping a table on luck.

Software

MapLibre GL JS (BSD-3) draws the city maps. DuckDB (MIT) and its spatial extension do the joins. The typeface is Jost by Owen Earl (SIL Open Font License), a free cousin of Futura, which it stands in for. The pipeline is Python with the standard library. The nomination texts were read for style by Claude (Haiku 4.5) inside Claude Code, and the site was built with Claude Code; every model-read tag is marked unverified until a person checks it.

Work studied

Open-source projects read while designing the pipeline, each the work of others. Licences as published; code under MIT, BSD, ISC or Apache may be reused with attribution, the rest was read for its ideas only.

Corrections

If a source is missing, misattributed or wrongly licensed here, say so and it will be fixed. The same goes for any number on the site: how the index works explains where each one comes from.