Updated 2026-09-30
Methodology and sources
Data as of
Two kinds of numbers
Almost every number on this site is computed: either from the Census data files bundled with the site, or from a stated formula such as the haversine distance, the WGS84 ellipsoid, or the SunCalc solar model. Computed numbers change only when the data files are rebuilt, and each page says which vintage it uses.
A small set of figures is quoted from an outside source, such as the Census definition of an independent city or NOAA's shoreline mileage. Each of those appears in the verification table below with its source link and the date it was last checked. If a figure could not be traced to an official source, it is not on the site.
Census data behind the county and state pages
The site ships one row for each of 3,144 county-equivalents in the 50 states and DC. Each row joins the 2024 Gazetteer (5 digit code, name, land area in square miles, internal point), the Vintage 2024 county population estimate for July 1, 2024, and the SAIPE 2023 median household income. State figures are sums of their counties, and density is population divided by land area.
- Census 2024 Gazetteer, counties
- Census Vintage 2024 county population estimates
- Census SAIPE 2023 state and county estimates
- Census Vintage 2024 subcounty population estimates and Census 2024 Gazetteer, places for place populations
- Census 2024 county adjacency file for bordering counties
- Census 2020 ZCTA to place relationship file for the ZIP codes on place pages
- Census 2024 cartographic boundary file, counties (1:5,000,000) for county and state outlines drawn by the site and the county finder
- Census 2024 Gazetteer, ZCTAs for ZIP code points
Rankings sort these values and break ties by FIPS code. Percentile phrases such as "top quarter" come from the same sorted lists. All Census files are US government works in the public domain. They were downloaded and last checked on 2026-09-30.
Towns and cities
Place pages cover the 10,255 incorporated places with 1,000 or more residents in the Vintage 2024 subcounty estimates. The whole-place population comes only from summary level 162 rows. The summary level 157 rows, which split a place by county, feed the "counties it spans" and "towns in this county" lists, so a city such as New York or Chicago counts once in full on its own page and in part on each county page. Places of 5,000+ (4,876 of them) are submitted to search engines; smaller ones have profile pages marked noindex.
Census-designated places, such as Urban Honolulu or Columbia, Maryland, are not in the subcounty estimates and are not listed. ZIP codes on a place page are the 2020 ZCTAs whose overlap covers at least 10% of the ZCTA's or the place's land. Growth is measured between the July 2020 and July 2024 estimates. Nearest places and city pairs are straight lines between 2024 Gazetteer internal points; each city of 100,000+ is paired with its 8 nearest peers, for 1,757 distance pages.
Time zones and ground elevation for the 342 cities of 100,000+ come from a single batched call to the Open-Meteo forecast API (IANA zone and Copernicus GLO-90 elevation at the internal point), cached at build time on 2026-09-30.
Center of population
The pin on the home page is an approximate mean center of population: the Census formula applied to 2024 county internal points. Latitude is the population-weighted mean of county latitudes. Longitude is weighted by population times the cosine of latitude. The result is 37.34° N, 92.28° W. The official 2020 point, computed from census blocks, is near Hartville, Missouri; county points are coarser, so the two differ by some miles.
Formulas
- Straight-line distance: haversine formula on a sphere of radius 6,371.0088 km, the mean radius (2a + b) / 3 of the WGS84 ellipsoid. See how distance is calculated.
- Degree lengths and UTM: the WGS84 ellipsoid. See miles per degree and UTM zones.
- Bearings, midpoints and rhumb lines: standard spherical formulas, each shown in its guide.
- Sunrise, sunset and twilight: the SunCalc library, with sunrise when the sun's center is 0.833° below the horizon, converted to local clock time with IANA time zone rules.
- Centers of population: county internal points weighted by population, with longitude also weighted by the cosine of latitude. See center of population.
Live services used by the tools
Some tools call outside services in the browser. If a service is down or rate limits a request (HTTP 429), the tool shows it as unavailable instead of a guess. Requests to each service are spaced at least one second apart, searches wait for typing to pause, and repeated geocoder searches are answered from memory. Usage terms: Photon, OSRM demo server (at most one request per second, no heavy use), FOSSGIS servers and Open-Meteo, all checked 2026-09-30.
- Map tiles: MapLibre GL with the OpenFreeMap style, from OpenStreetMap data (ODbL).
- Place search and reverse lookup: the Photon geocoder, from OpenStreetMap data.
- Drive times and road distance: the public Valhalla instance, with the OSRM demo server as a fallback. If both fail, no driving number is shown.
- Elevation: Copernicus GLO-90 through the Open-Meteo elevation API.
- World boundaries: Natural Earth 1:50m, public domain. US county and state outlines: Census cartographic boundaries through us-atlas 3.0.1.
Files you open in the map tools, such as CSV, GPX, KML and GeoJSON, are read in your browser and are not uploaded.
Known issues
- Place data: the subcounty estimates cover incorporated places only, so census-designated places are missing from towns lists, place pages and the radius tools. ZIP code lists use the 2020 relationship file, which predates later annexations.
- Outlines: county shapes are simplified for the web, so a point within a few hundred meters of a county line can test on the wrong side. State outlines in the browser tools still come from us-atlas 3.0.1; state lines have not changed since.
- Vintage: population is Vintage 2024. Census lists Vintage 2025 as its most recent set.
- The park finder lists the 63 national parks on the National Park Service system list, checked by name and link on 2026-09-30. Each park is ranked from one approximate interior point. The countries listed on the geographic line pages are computed: points every 0.02° along each line are tested against the Natural Earth 1:50m outlines, so islands too small for that scale drop out.
Verification table
Every figure on the site that is quoted rather than computed, with the source it was checked against and the date of the check.
| Figure | Value | Source | Checked |
|---|---|---|---|
| WGS84 semi-major axis and flattening | a = 6,378,137 m; 1/f = 298.257223563 | NGA, WGS 84 defining parameters | 2026-09-30 |
| International mile and foot | 1 mile = 1,609.344 m; 1 foot = 0.3048 m | NIST, revised unit conversion factors | 2026-09-30 |
| Distance per degree at 38° N (USGS rule of thumb) | Latitude: 69 mi, 1.15 mi per minute, 101 ft per second. Longitude: 54.6 mi, 0.91 mi, 80 ft | USGS FAQ | 2026-09-30 |
| UTM zone layout | 60 zones, each 6° of longitude, numbered 1 to 60 eastward from 180° | USGS FAQ: what does the term UTM mean? | 2026-09-30 |
| Census regions and divisions | 4 regions, 9 divisions, state membership as listed on region pages | Census Bureau regions and divisions map | 2026-09-30 |
| County-equivalent types | Louisiana parishes; Alaska boroughs, city and boroughs, municipalities and census areas; independent cities in MD, MO, NV and VA; DC as one unit | Census Bureau geography glossary | 2026-09-30 |
| Internal point and land area definitions | Internal point is usually the centroid, moved inside the area when needed; intermittent water, glacier and swamp count as land | Census Bureau geography glossary | 2026-09-30 |
| Gazetteer fields | ALAND and AWATER in square meters, ALAND_SQMI in square miles, INTPTLAT and INTPTLONG in decimal degrees | Census Gazetteer record layouts | 2026-09-30 |
| Connecticut planning regions | Nine councils of governments adopted as county-equivalents in 2022 | Census Bureau substantial changes to counties | 2026-09-30 |
| Alaska census area split | Valdez-Cordova (02261) split into Chugach (02063) and Copper River (02066), effective January 2, 2019 | Census Bureau county changes, 2010s | 2026-09-30 |
| Population estimate method and vintages | Births, deaths and migration since the last census; each vintage supersedes earlier ones; reference date July 1; Vintage 2025 is the latest completed set | Census Bureau population estimates program and county totals | 2026-09-30 |
| SAIPE scope and method | County and state income and poverty estimates modeled from survey data, population estimates and administrative records, with the ACS as survey input | Census Bureau SAIPE program overview | 2026-09-30 |
| ZCTA definition | Built from census blocks; each block gets the ZIP Code most common among its addresses | Census Bureau ZIP Code Tabulation Areas | 2026-09-30 |
| 2020 US center of population | 37.415725° N, 92.346525° W, near Hartville, Missouri (594 residents); 11.8 miles west and south of the 2010 center | Census Bureau centers of population | 2026-09-30 |
| State shoreline mileage | 30 states from Alaska (33,904 mi) to Indiana (45 mi); US total 95,439 mi including territories | NOAA Office for Coastal Management, shoreline mileage of the United States | 2026-09-30 |
| National parks | 63 national parks, names and NPS links as listed in the park finder | National Park Service, National Park System units | 2026-09-30 |
Licensing
Census Bureau and NOAA works are US government works in the public domain. Natural Earth is public domain. OpenStreetMap data is ODbL. Copernicus and Open-Meteo require attribution. Online Map Tools is independent and not affiliated with any of these publishers. Blank map SVGs on this site are offered as CC0.
Questions people ask
How current is the data?
Population is Census Vintage 2024 (July 1, 2024), land area and internal points are the 2024 Gazetteer, and income is SAIPE 2023. Census has since published Vintage 2025, which this site does not yet use.
Are any numbers estimated by this site?
No figure is guessed or filled in. Missing values, such as a county with no SAIPE income estimate, are shown as unavailable and left out of rankings.
How do I report a wrong number?
Use the error report link at the bottom of any page, or email hello@sajam.dev. Corrections are made at the source file and every page that reuses the figure updates with it.