This site is a nonpartisan reference. Every figure on it comes from a public source, and this page lists those sources, how often each is refreshed, and where the data has known limits. If you find something wrong, the contact page is the fastest way to reach us.
District boundaries and maps
District outlines come from the U.S. Census Bureau TIGERweb boundary files for the 119th Congress. The base map underneath each outline is drawn from OpenStreetMap. Both attributions appear in the caption under every district map.
Boundaries reflect the districts in use through the current Congress. They are not a projection of what the lines will look like after the next election.
ZIP codes and district assignments
ZIP code assignments come from the Census Bureau Block Equivalency File for the 119th Congress, dated July 30, 2024. That file maps census blocks to congressional districts, which is how a ZIP code can be matched to one or more districts.
ZIP codes are mail delivery routes. They were never designed to match political boundaries, and many of them do not. Each district page states how many ZIP codes the district contains and how many of those also fall inside a neighbouring district, with specific examples. As one illustration, ZIP 90210 spans three California districts.
The full crosswalk is published as an open file: ZIP code to congressional district, covering all 33,774 ZIP codes as CSV, JSON and an endpoint. 7,299 of them fall in more than one district.
Address lookup
The lookup tool sends the address or ZIP code you enter to the official U.S. Census geocoder, which returns the matching district. A full street address gives an exact answer. A ZIP code on its own can return more than one district, and when it does the tool shows every possibility rather than guessing.
Members of Congress
Representative and senator records are checked against three sources: the Clerk of the House member list, the Senate.gov member list, and the unitedstates/congress-legislators dataset. Where those sources disagree, the chamber’s own list is treated as authoritative.
The most recent full audit ran on September 3, 2026. It compared all 435 district pages, all 100 senator pages and all 50 state pages against those sources. Tenure dates on district pages show how long the member has represented that specific district, and separately how long they have served in the House, because 88 members currently differ on those two dates after changing districts.
Elections and candidates
Candidate listings for the 2026 races come from Federal Election Commission filings. The FEC lists everyone who has filed to run. It does not show who won a primary, so an FEC count is a count of filers rather than a ballot.
The partisan lean figure shown on district pages is the 2024 presidential margin in that district, sourced from The Downballot.
Population figures
District population comes from the 2020 Census, which is also the apportionment used to divide the 435 seats among the states. Each district represents roughly 760,000 people.
Known limitations
- A ZIP code alone does not always identify one representative. Use a full street address when the answer matters.
- Ten states changed their congressional maps between censuses during the 2025 to 2026 cycle: Alabama, California, Florida, Louisiana, Missouri, North Carolina, Ohio, Tennessee, Texas and Utah. Pages for those states carry a notice, and the redistricting tracker lists what changed in each one. The new lines take effect with the November 2026 election.
- 2 House seats are currently vacant, Florida 20 and Texas 23. Their pages show the district and its boundaries but no sitting member.
- Official chamber rosters are published on their own schedule and can lag a resignation, death or special election by days or weeks.
- Census boundary files are updated between Congresses, not continuously.
Corrections
If a figure here is out of date or wrong, we want to know. Send the page address and what looks incorrect through the contact page. Corrections to member records, district assignments and election dates are made as soon as they can be checked against the sources listed above.
How this site stays nonpartisan and handles corrections is set out in our editorial standards.