Transparency

Sources & methodology

ZipElm compiles public data. We do not collect it ourselves: every figure comes from the sources listed here, and we are not an official source.

Data we show and where it comes from

What	Source	Period
Population	U.S. Census Bureau, 2020 Census (Demographic and Housing Characteristics, table P1)	2020
Households, employment rate	U.S. Census Bureau, American Community Survey 5-year Data Profiles (DP02, DP03)	2020–2024
Median household income, median age, bachelor's degree or higher, health insurance coverage	U.S. Census Bureau, American Community Survey 5-year Subject Tables (S1901, S0101, S1501, S2701)	2020–2024
Housing units	U.S. Census Bureau, American Community Survey 5-year Detailed Tables (B25002)	2020–2024
ZIP code areas, their centers and land area	U.S. Census Bureau, ZIP Code Tabulation Areas (TIGER/Line)	2025 files
ZIP code types (standard, PO Box, unique) and city names	USPS ZIP code classifications and public ZIP code reference data	Current at build
City and county boundaries	U.S. Census Bureau, cartographic boundary files and TIGER/Line	2020 / 2025 files
Lakes, bays and rivers on maps	U.S. Census Bureau, TIGERweb hydrography	Current at build
Neighboring countries on maps	Natural Earth (public domain)	1:10m
Interactive map base layer (after you select “View interactive map”)	© OpenStreetMap contributors	Live
State flags	Wikimedia Commons	—

Area codes and time zones come from public geographic reference data. “Period” is the survey or file year. The figures on this site were last refreshed on September 27, 2026; city and state pages show that date next to their statistics.

How we calculate things

Density is residents divided by land area in square miles (2020 Census land area; water is not counted).
Share of the state is a city's residents divided by its state's residents (2020 Census).
Rankings compare a city with the other cities in our dataset, in its state and nationwide. They are not a ranking of every U.S. city.
Map colors show each ZIP code's residents per square mile, split into up to five classes by the quantiles of that city's own ZIP codes. The legend on each map shows its ranges, so colors are not comparable from one city to another.
Which ZIP codes belong to a city: we group them by the city name USPS prints on that ZIP's mail and, for places with no postal name of their own, by geographic overlap. About explains the details.

What the data can't tell you

ZIP codes are mail routes, not neighborhoods. Census areas only approximate them and can cross city or county lines.
Income, age, education and health coverage are survey estimates with a margin of error, larger in small areas.
When the Census does not publish a figure, we show a dash instead of guessing.

The full list is in What to keep in mind on the About page.

We are not an official source

ZipElm is an independent site. It is not affiliated with, sponsored by or endorsed by the United States Postal Service, the U.S. Census Bureau or any government agency. “ZIP Code” is a registered trademark of the USPS. For official ZIP code and address information, use the USPS ZIP Code Lookup; for official statistics, use census.gov. See also our Terms of Use.

Corrections

Found something that doesn't match the original source? Write to contact@zipelm.com with the page address and we will check it against the data.