All three levels follow, one after the other. Brief · Detailed · Super detailed
Brief One line per page. About a minute.
Leaderboards
The home page ranks U.S. cities by how much recognised historic architecture they have for their size.
Search & explore
Search every listing in your own words or with the grid, and see the cities ranked for exactly what you chose.
Plan a tour
Turn what you like into stops on a map: in a city you're visiting, or along a drive you're taking.
Search inside the documents
A sentence in Explore also searches the photographs, plans and maps inside the nomination files.
Styles
Every architectural style as a tree, each with a page ranking the cities that have the most of it.
How it works
The rules behind every number: what is counted, how a listing is placed in a city, the measures and the limits.
Roadmap
What works now, what is being built next, and when the links marked coming soon will open.
Detailed A short paragraph per page, pointing at the main controls.
Leaderboards
The leaderboard ranks cities by National Register listings, comparing each city only with cities of a similar population. Choose what to rank in the grid of squares under the search (a style, a collection such as National Historic Landmarks, buildings or districts, a city size), change the measure with Ranked by, and pin a city to keep it at the top while you compare. Click any row to open that city's panel with a map and every listing behind the number.
Search & explore
Explore starts with every National Register listing and narrows as you choose. Type a sentence such as round barns in Indiana and the parts it understands (a state, a city, an architect, years) become filters you can see and remove; the listings are ranked by how well they match the rest. Or use the grid to filter by style, type, significance, area, place and evidence. The counts update as you choose, and the cities ranked for that exact selection sit beside the listings.
Plan a tour
Plan a tour has two modes. A city I'm going to: pin one city or several and choose what you want to see in the grid, and every matching listing becomes a numbered stop on a map in driving order, with a Google Maps route and a link you can send. A route I'm taking: paste a directions link from Google Maps, Apple Maps or Waze, or type a start and an end, and see the National Register places along the way; add the ones you want and the drive is routed through them.
Search inside the documents
Every National Register nomination is a scanned document with photographs, site plans, floor plans and maps. When you search with a sentence in Explore, Photos and plans appears above the listings with the pages that look most like what you described, searched by what they show rather than by their words, including pages whose text could not be read. Choose Photographs, Maps and plans or Any page.
Styles
Styles lists every style the index knows as a tree: families such as Late Victorian or Modern Movement, with the styles beneath them. Each has its typical United States period and how many cities rank for it.
On the Modern Movement style page:
A style page, here Modern Movement, starts with what the style is, its period and where it sits among the others. Then come the top cities in every size class, ranked by listings per 10,000 residents (adjusted), each with a link to all the cities of that size, and the cities with too few listings to rank.
How it works
How it works sets out the rules. A listing counts for a city when its coordinate falls inside the city's legal boundary. Cities compete only within the Census Bureau's size classes. The measures, the adjusted rate and the ranking rules are defined here, along with every source and its date, and the known limits.
Roadmap
The roadmap says what the site does today, what is in progress (live exploration, facts about the buildings, a map to travel with, architecture along the way) and what is coming (human verification, accounts, adding and correcting listings, a forum). Links on the site marked coming soon point here.
Super detailed Every control, a worked example, where the data comes from and its limits.
Leaderboards
The search box. Describe the places you want in a sentence and press Search. A sentence searches the listings themselves, so it opens Search & explore with your words; the same box is in the same place on every page.
The grid of squares. Nine squares set what is ranked. Style (the big square) picks one style or several; a family such as Modern Movement counts every style beneath it. Type picks buildings or districts. Significance holds the level and the named collections (National Historic Landmarks, Criterion C, Mid-century modern and the rest). Where holds the state and the city size; the leaderboard uses the city size as its size class. Level, Area, State and Evidence can be set too, but a leaderboard cannot rank by them: a line under the search says what is not used here, with a link that opens your whole search in Explore. Collapse filters folds the grid into one line of pills.
Example searches. Under the grid, four example sentences (round barns in Indiana, Carnegie libraries by Patton and Miller, Art Deco movie theaters, Prairie School houses in Minnesota) each open Search & explore with that search.
Pin a city. Type a city in Find a city to pin and choose Pin to top: it stays at the top of the board so you can compare it with every row. Near me pins the city you are in, or the nearest ranked city, if you let the browser share your location. A name that is not a ranked city is searched in Explore instead.
Ranked by. The measure. The default is listings per 10,000 residents, adjusted so a town with three listings can't top the table on luck; the raw rate is beside it on every row. You can also rank per square mile, by historic buildings per 100 housing units, or by the composite percentile within each size class.
The rows. Each row is one city: its rank, a mini-map of its listings, its population and land area, how many places it has in the category, a bar against the leader, and the measures. With every size class shown, each row is tagged with its class. Click a row, or its count of places, to open the city's panel.
The city panel. The panel shows the city's listings on a map and in a list. Lenses (Traveller, Architect, Researcher, Archivist, Nominator, City official) change what is shown under each name and the order, never which listings or the rank. From the panel you can start a tour (Build your tour) or download the records as CSV. Open it by clicking any row.
Browse the leaderboards. At the foot of the page, every named category and every style family has its own rendered leaderboard page, one table per size class.
Worked example: round barns in Indiana. Type round barns in Indiana in the box and press Search. A round barn is a building form, not one of the styles the leaderboard ranks, so the sentence goes to Search & explore, which searches the listings themselves. That is the next stop.
Where the data comes from. National Register listings from the National Park Service's listed-properties spreadsheet, placed by the NPS map service coordinate (Census address geocoding fills gaps). Population, housing units, boundaries and land area from the U.S. Census Bureau (ACS 5-year, TIGER/Line, Gazetteer). Styles from the nomination forms, the Register's own index, Register Atlas, Wikidata and a model reading of the nomination texts.
Limits. Only cities of 10,000 or more residents with at least 5 listings in the category are ranked; smaller counts are shown but not ranked. The Register's 50-year rule means recent architecture is under-counted. Style tags read by a model are marked inferred until a person checks them. About a quarter of all listings sit outside any city limit and count for their county only.
Search & explore
The sentence. Type what you want and press Search. What the search understood is shown under the box as pills: remove one to drop that part. Only what you named outright is applied; anything ambiguous is offered for one tap instead.
The grid. The same nine squares as every page, all of them used here. Tap a square to open its options, with a count beside each. Style, Type, Area and the rest let you pick several; press Apply to use them. Choices in one square are any of; choices in different squares must all hold. The selection is in the page's address, so every view is a link you can share.
The count. How many listings match, updated as you change the search or the grid.
Show. Listings + ranking shows the listings with the ranked cities beside them; Ranked cities only shows the whole ranking as a table, size class by size class.
The ranked cities. Cities of 10,000 or more with at least 5 matching listings, ranked within their size class. Choosing a city narrows the listings to it; the arrow beside it opens that city in the leaderboards or its listings. With two or more styles chosen, Pooled counts every listing in any of them together, and Blend ranks each style on its own and averages the scores. On a phone the ranking is a strip that opens as a sheet.
The listings. Fifty at a time, with More for the rest. Each shows its photograph from the nomination where there is one, its place and type, its build years and architects with where each came from (unchecked when read from the nomination by a model), and its style tags. The name opens the listing's record on NPGallery, the National Park Service's archive.
Worked example: round barns in Indiana. Search round barns in Indiana. Indiana becomes a pill you can remove, and the listings are ranked by how well they match round barns. The ranked cities beside them show which Indiana cities have the most of what matched; choose one to see only its listings. The same sentence also searches the photographs and plans in the nominations, which is stop 4.
Where the data comes from. Every listing in the National Register, answered live by the site's own query service from the same data as the leaderboards. Build years and architects come from Register Atlas, Wikidata and a model reading of the nominations; styles as on the leaderboards. Claude reads your sentence into the filters you see.
Limits. Explore is marked preview. Facts read from the nominations are unchecked: a hand check of a sample found about 9 in 10 right, and wrong build years are the usual error. A city is ranked only with at least 5 listings in the selection. The first search after a quiet spell can take a few seconds while the service starts.
Plan a tour
Two modes. A city I'm going to, or A route I'm taking. The page keeps one set of boxes on screen at a time.
The grid. What the stops match: collections, styles, and buildings or districts. City size and the other squares are kept but not used here, and the line under the search says so, with a link to the whole search in Explore.
Pin cities. In A city I'm going to, Find a city to pin and Pin to top add a city; you can pin several. Near me adds the one you are in, if you share your location.
The stops. Every matching listing in the pinned cities, numbered in shortest-next-stop order on a map. Open the route in Google Maps (in legs of eleven stops), copy a link to the tour, download a PDF or print it.
A route I'm taking. Paste a directions link, or switch to typing a start and an end. A link with no start asks where you're starting from. Choose how far from the route to look (5 to 100 miles) and how many stops to suggest (none to 15). Tick Visit several places at each stop to walk or drive between a few places at each, with a time limit between them and an option for a longer scenic walk. Send the trip to Google Maps or Apple Maps, copy a link, download a PDF or print.
Worked example: round barns in Indiana. Round barns are not a style or a collection, so Plan a tour can't pick them by name: carried over from Explore, your search shows under the box as not used here, with a link back to it in Explore. A tour plans from what the grid holds, such as a style in the cities you pin. For a drive, choose A route I'm taking and type Chicago, IL to Columbus, IN.
Where the data comes from. Stops are National Register listings at their NPS map-service coordinate. Routes are worked out by the site's own routing service; place names you type are looked up with OpenStreetMap's Nominatim; the maps are OpenFreeMap tiles. A pasted link is read in the page and never stored.
Limits. A listing without a public coordinate is left off the map, and the page says so. Addresses the Register withholds are never located. Stops along a route are suggested only where they make sense: none near the start or the finish, and none on a drive under 200 miles.
Search inside the documents
Where it is. The old Search inside the documents page now opens Explore: there is one search box, and a sentence searches the listings and the nomination pages together.
Photos and plans. Shown once you search with a sentence: up to twelve pages, each linked to the full image. Listings whose pages matched also move up in the list below.
Kind of page. The menu beside the heading chooses Photographs, Maps and plans, or Any page.
Starting up. The photo search starts when you open Explore and shuts down when nobody is using it, so the first search can take a moment; a line says when it is starting or loading.
Worked example: round barns in Indiana. Search round barns in Indiana with Photographs chosen: the pages that look like round barns come up from the Indiana nominations, and the listings they belong to move up the list.
Where the data comes from. The scanned nomination documents, as the National Park Service and the states publish them. Pages are indexed by an image model so they can be found by what they show.
Limits. Photos and plans cover 18 states so far: the Great Lakes states and the Northeast (CT, DC, DE, IL, IN, MA, MD, ME, MI, MN, NH, NJ, NY, OH, PA, RI, VT, WI). More are being added state by state. Copies a source allows only for non-commercial use are searched but never shown.
Styles
The tree. Families first, then movements, styles and variants beneath them. A family counts every style beneath it: Modern Movement includes Art Deco, International Style and Brutalism, and each is also its own page. Beside each, its typical period and how many cities rank, or how many have some if none has five yet.
Every style has a page. A style is ranked once a city has five listings in it; until then its page lists the cities that have some.
On the Modern Movement style page:
What the style is. The definition, the typical period, the family it belongs to and the styles it includes, each linked.
How it is ranked. How many cities rank and how. Open in the explorer re-ranks by another measure or compares categories; open it live in Explore narrows it with the whole grid.
One table per size class. The top ten cities of each Census size class, each row with its rate, the raw rate and the other measures. The city's name opens it in the leaderboards with the city pinned; All the cities of this size, ranked, opens the full table for that class.
Below the ranking floor. Cities with one to four listings in the style, by count: too few to rate fairly, so listed but not ranked.
Worked example: round barns in Indiana. A round barn is a building form, not an architectural style, so it has no style page: search for it in Explore instead. A barn whose style is recorded counts on that style's page like any other listing.
Where the data comes from. A controlled vocabulary of about ninety style terms, each with its typical U.S. date range and Wikidata identifier. A listing's styles come, in order of trust, from the nomination form's Architectural Classification, the NRIS style code and the NPS Atlas, then Wikidata, then a model reading of the nomination text that must quote the sentence each style rests on.
Limits. Model-read and Wikidata tags are inferred: they count unless their confidence is low, and they are marked not yet verified until a person checks them. Narrow style pages carry a coverage note on how many of their cities are in states whose nominations have been read.
How it works
What is counted. A National Register listing: a building, district, site, structure or object, including National Historic Landmarks. About 100,800 listings.
Which city a listing belongs to. By its coordinate inside the city's Census boundary, with rules for listings near a boundary and for withheld addresses. About a quarter of listings sit outside any city.
Size classes. The seven Census size-of-place classes from 10,000 residents up. Places under 10,000 are mapped but not ranked.
Measures. Per 10,000 residents, per square mile, historic buildings per 100 housing units, the composite percentile, and the adjusted rate, which is the default.
Ranking rules. At least 5 listings in the category to be ranked; below that the count is shown with the places behind it.
Tags. Official tags come straight from an NPS field; inferred ones carry a confidence; verified and rejected ones were checked by a person and override the rest.
Worked example: round barns in Indiana. The Indiana cities that come up for round barns are placed and ranked by exactly these rules: each barn counts for the city whose boundary holds it, and a barn outside every city limit counts for its county only.
Where the data comes from. Every source, with the date of the data used, is listed under Sources and vintages: the National Park Service, the U.S. Census Bureau, Register Atlas, and Wikimedia Commons and Wikipedia for display only.
Limits. The page ends with the known limits: the 50-year rule, how common the Architecture tag is, withheld addresses, gaps in style and build-year data, and how many listings have a photograph.
Roadmap
Now. What works today.
In progress. Each Next section says what is built so far, with dates, and what is still to come.
Coming soon. Human verification of the style tags, accounts, adding and correcting listings, and a community forum. The verify, Create an account and Missing a place links lead here until they open.
How the order is decided. Why the work is done in this order.
Worked example: round barns in Indiana. Searching by what a building is (a barn, a church, a school) rather than by its style is part of facts about the buildings, which is in progress: Indiana's nominations have been read for use, build year, architect and materials.
Where the data comes from. The roadmap is written by the people building the site and updated when work lands or plans change.
Limits. Dates and plans change. Anything marked coming soon is not open yet; the page says so rather than promising a date.