How the figures are made

Where every figure comes from

• American Community Survey, 2020-2024 5-year estimates (released January 2026): 57 measures from the Data Profiles (DP02, DP03, DP04, DP05) for every state, county, place and census tract, each with its published 90% margin of error.
• American Community Survey, 2015-2019 5-year estimates: the same measures for states, counties and places, used only for the change between the two periods. Tracts were redrawn in 2020, so tract figures are not compared across the two periods.
• 2020 Census, P.L. 94-171 redistricting data: the full count of residents and housing units for every geography.
• Population estimates, Vintage 2025: the Census Bureau's estimates for July 1 of 2020 to 2025 for states, counties (with Puerto Rico and its municipios, from the Bureau's Puerto Rico files), incorporated places and the towns and townships of the states where they govern. Census-designated places get no yearly estimate.
• Building Permits Survey: housing units in permits issued by each permit office, annual files 2019-2025, for places and counties.
• Population history: the Census Bureau's intercensal estimates for 2000-2010 and its Vintage 2020 estimates for 2010-2019 (made before the 2020 Census, not revised to it), for places, towns and counties, and the 2010 Census count.
• Metropolitan areas: the Census Bureau's delineation of metropolitan and micropolitan statistical areas, July 2023 (list 1), naming the area each county belongs to.
• Tract boundaries: the 2024 cartographic boundary files at 1:500,000, for each tract's outline and the tracts that border it.
• Towns and townships: the same ACS Data Profiles, 2020 Census counts and population estimates at the county-subdivision level, with the 2024 county-subdivision Gazetteer.
• Geography: the 2024 Gazetteer files (land area, internal points), the 2020 place-by-county file (which counties a place lies in), the 2020 block assignment files (which places a tract's blocks belong to) and the 2024 cartographic boundary files (the outlines on the locator maps).

PlainCities publishes 32,330 places, 3,222 counties and 85,382 census tracts: every one the Census Bureau publishes for 2020-2024 in the 50 states, the District of Columbia and Puerto Rico. It adds 16,088 towns and townships: the county subdivisions with an active local government in the 20 states where the Census Bureau estimates towns and townships every year: everywhere in Connecticut, Maine, Massachusetts, Michigan, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont and Wisconsin, and in the counties of Illinois, Indiana, Kansas, Missouri, Nebraska, North Dakota, Ohio and South Dakota that are organized into townships. A subdivision that covers the same area as a place already listed is not listed twice. Subdivisions without a government (the census county divisions of the other 30 states, unorganized territories, inactive townships) are statistical areas and are not listed.

This product uses the Census Bureau Data API but is not endorsed or certified by the Census Bureau.

The checks, and when they last ran

A scripted pipeline downloads each file from the Census Bureau, loads it and rebuilds the database. The release stops if any check below fails. The data editor (a role carried out with AI agents and scripts by the studio that publishes PlainCities) runs them before every release of the database and reads the results. Last run: 2026-10-09.

Oversight by page class: place, county and state records are covered by the completeness, spot and identity checks above at every release; census tract records by the completeness and spot checks; rankings and research pages are computed from the same database at request time, and their methods are stated on each page; for the October 2026 release the publisher's AI agents also re-read figures from the rendered pages of every page type against the Census Bureau's API (39 figures on 13 page types, none differed), opened each page type in a browser at five widths in both themes, and had the site reviewed in six roles (a quality rater, a spam analyst, a competing publisher, an answer engine, a claims and legal reader and a designer) by separate AI reviewer agents that had not built the pages; no human outside the publisher has reviewed the site.

How uncertain figures are handled

Survey figures are estimates. PlainCities shows each one with its 90% margin of error and computes its coefficient of variation (the margin divided by 1.645, divided by the estimate). An estimate with a coefficient of variation above 40% is marked with a ring and never ranked. Two figures are called different only when their gap exceeds 1.645 times the square root of the sum of their squared standard errors, the Census Bureau's test at 90% confidence; the test leaves out the small correlation between overlapping samples, which makes it slightly conservative.

How change since 2015-2019 is measured

The two five-year periods do not overlap, which is the comparison the Census Bureau recommends. Dollar figures from 2015-2019 are multiplied by the ratio of the Bureau of Labor Statistics' R-CPI-U-RS annual averages for 2024 and 2019 (1.2307), the index the survey itself uses for inflation. A change is shown only when both estimates are reliable and the gap passes the 90% test; otherwise the page says the margins cannot tell the periods apart.

How ranks are computed

A place is ranked among its state's places that had 1,000 or more residents in the 2020 Census and whose estimate is reliable; a tract among its county's tracts with a reliable estimate. Equal published figures share a rank. Growth ranks use the Census Bureau's population estimates (incorporated places only). National rankings state their own set of places and minimum size on the page.

Which rows get their own page

A place, town or census tract gets its own page when two things hold: at least 8 of 10 core figures (population, median age, median household income, per capita income, poverty rate, bachelor's degrees, owner-occupied share, median home value, median gross rent and travel time to work) are published with a coefficient of variation of 40% or less, a share of exactly 0% or 100% not counting; and at least half of all its figures that the survey publishes for its state are that reliable. It also needs to be an area of its own: a tract that is the whole of one place, or the only tract of its county, is a row of its county's tract table, since the place or county page already gives its figures. A page readers already find through search keeps its own page. Every other place is a row of its county's places table (its 2020 Census count, its survey population with margin, income, home value, poverty rate and share in the county) and every other tract a row of its county's tract table (2020 count, population, income, home value, rent, poverty); its old address leads to that row. In this edition 30,371 places and 80,478 tracts have their own page.

How the site is built

PlainCities' publisher uses AI tools to write the pipeline, the page templates, the sentences that describe each place and the research write-ups. The numbers in every sentence come from database queries, and each sentence is written only when its figures exist and are reliable; no figure is typed by hand. AI does not decide any figure, rank or significance call: those come from the Census files and the rules above.

What a census figure leaves out

• ACS figures describe a five-year period, not a single year; for places that changed fast they lag.
• Small places and many tracts rest on a few dozen sampled households; read their margins first.
• Home values are owners' own estimates, not sale prices; rents include utilities the tenant pays.
• A permit is not a finished home, and permit offices sometimes report part of a year.
• PlainCities does not publish crime, climate, school or cost-of-living figures; each place and county page links the official source for crime, climate and schools.

What PlainCities covers, and what it leaves to others

PlainCities covers the census record of a place: people, households, income, housing, growth and building, from the state down to the census tract. It does not publish ZIP code areas (a postal geography the Census Bureau tabulates separately) or the figures of other subjects; links to those go to the official sources.

Who answers for it

The publisher named on the about page answers for the site. Report an error to hello@plaincities.com: it is traced to the source file, fixed in the pipeline if the pipeline is at fault, and listed on the corrections page.