List of United States congressional districts

Structure and apportionment

Allocation of seats to the states is determined by population counts produced by the Bureau of the Census in the decennial census. After each census the process of apportionment distributes the fixed 435 voting seats among the 50 states according to population. The total number of voting seats has been fixed at 435 since the Reapportionment Act of 1929, with a brief exception when Alaska and Hawaii were admitted and the House temporarily increased to 437.

Redistricting and legal framework

Once a state knows how many seats it will have, it undertakes redistricting to draw district boundaries. States have discretion over methods and criteria, so long as plans comply with constitutional protections and federal statutes. Redistricting may be required when apportionment changes a state's delegation size, or it may be undertaken periodically to reflect changes in population distribution and demographics. Courts often review and sometimes reject maps for reasons such as racial discrimination or violations of equal population requirements; controversies over partisan gerrymandering have produced extensive litigation and reform efforts.

Contents of a comprehensive list

A complete compendium of U.S. congressional districts typically includes several elements:

• All 435 current voting districts, identified by state and district number.
• Non‑voting delegations representing territories and the District of Columbia.
• Obsolete districts: historical districts that have been eliminated or renumbered through reapportionment and redistricting.
• Notes on unique cases, such as states that elect at‑large representatives when they have a single seat.

History and development

The practice of electing representatives from geographically defined districts has evolved since the early Republic. Apportionment methods, congressional size, and legal standards for equal representation have changed over time. Notable historical points include the periodic adjustment of House size prior to 1913, the 20th‑century decision to fix the House at 435 members, and the continuing impact of census data such as the 2010 United States Census on district maps.

Importance and practical uses

District lists serve multiple audiences: voters seeking their representative, scholars analyzing political geography, and officials administering elections. Practical items in such lists often include district boundaries, population counts, past election results, and links to state redistricting authorities. For concise definitions and administrative details consult resources on congressional districts and related processes via authoritative portals such as those that document how congressional districts are formed and maintained, or state electoral offices and the census bureau for population data and map files. Additional guides explain how individual states implement redistricting and where to find historical district information.

Readers looking for a full enumeration can expect a current list of 435 districts plus entries for over 200 obsolete districts and the current non‑voting delegations; many compiled lists also include links to official maps, historical notes, and references to relevant litigation and legislation that shaped district lines.