A congressional district is a geographic area within a single state whose voters elect one member to the U.S. House of Representatives. Federal law caps the House at 435 voting seats, divides them among the states after each decade’s census, and requires every state with more than one seat to split itself into single-member districts of roughly equal population.1Office of the Law Revision Counsel. 2 USC 2c Each district elects one representative, and each representative must live in the state they represent, though not necessarily inside the district itself.2Cornell Law Institute. U.S. Constitution Annotated Article I Section 2 Clause 2 Qualifications of Members of the House of Representatives
The whole system rests on a single principle the Supreme Court laid down in Wesberry v. Sanders (1964): “as nearly as is practicable, one man’s vote in a congressional election is to be worth as much as another’s.”3Justia Law. Wesberry v. Sanders, 376 U.S. 1 (1964) That “one person, one vote” standard is why districts have to be redrawn after every census and why their populations have to line up so tightly.
How Many Districts Each State Has
The Constitution requires a population count every ten years, and the Fourteenth Amendment tells states to count “the whole number of persons” for the purpose of dividing House seats.4Library of Congress. Fourteenth Amendment Section 2 After the census, the 435 seats are divided among the 50 states using a formula called the method of equal proportions, codified at 2 U.S.C. § 2a. The formula works to minimize percentage differences in each state’s share of representation relative to its population.5Office of the Law Revision Counsel. 2 USC 2a – Reapportionment of Representatives Every state is guaranteed at least one seat, and the remaining 385 are handed out based on population.6United States Census Bureau. About Congressional Apportionment
Because 435 is fixed, apportionment is a zero-sum exercise. When fast-growing states pick up seats, slower-growing states lose them. The most recent reallocation, based on the 2020 Census, shifted seats among several states and will stand through the 2030 count.7United States Census Bureau. Congressional Apportionment
Six states have populations small enough to warrant only a single representative: Alaska, Delaware, North Dakota, South Dakota, Vermont, and Wyoming.8United States Census Bureau. About Congressional Districts Each functions as one at-large district, with the representative elected by voters statewide. There are no internal lines to draw.
How District Lines Get Drawn
Once a state knows how many seats it will have, it must draw boundaries to match. Redistricting typically happens in the year or two after each census, using the new population data.9United States Census Bureau. About the Decennial Census of Population and Housing
Who Draws the Maps
In most states, the state legislature draws congressional maps, usually subject to the governor’s veto. Roughly a dozen states have shifted some or all of that authority to independent or bipartisan commissions, and a handful use hybrids where a commission drafts maps but the legislature still signs off. The push for commissions rests on an obvious conflict of interest: legislators picking their own voters. Whether commissions produce fairer maps is debated, but they have become more common as voters in several states have approved ballot measures creating them.
Equal Population, District by District
The Supreme Court set a demanding bar for population equality in congressional maps. In Kirkpatrick v. Preisler (1969), the Court rejected any notion that small population differences are automatically acceptable. A state has to show a good-faith effort at “precise mathematical equality” and justify every variance, no matter how small.10Justia Law. Kirkpatrick v. Preisler, 394 U.S. 526 (1969) With modern mapping software, most states now produce congressional districts that differ by zero or one person. The standard for state legislative districts is looser, but for the U.S. House, the tolerance is essentially nil.
Traditional Criteria
Beyond raw population equality, map drawers work within a set of traditional principles. None is a blanket federal requirement. They function as best practices that courts look at when deciding whether a map was drawn for legitimate reasons or for manipulation:
- Compactness. Districts should be reasonably compact, without bizarre tentacles stretching across the state.
- Contiguity. Every part of a district should connect to every other part without cutting through another district. About 18 states write this into law, and nearly all follow it in practice.
- Preserving political subdivisions. Counties, cities, and towns are kept whole where possible.
- Communities of interest. Populations with shared economic, social, or geographic ties are grouped so they can advocate through a single representative. A farming region, an urban core, or a tribal community are typical examples.
These criteria get weighed against each other, and no formula dictates the weights. That ambiguity is exactly what gives map drawers room to shape outcomes.
Gerrymandering and the Limits on It
Gerrymandering is the deliberate manipulation of district lines to lock in an advantage for a party or group. The mechanics come down to two words. Cracking spreads an opposing group’s voters across several districts so they fall short of a majority everywhere. Packing jams them into as few districts as possible; those seats are won by landslides, but the group’s influence is wasted elsewhere. Combining the two can turn a modest statewide majority into a lopsided share of House seats.
Racial gerrymandering runs into hard constitutional limits. Under the Fourteenth Amendment’s Equal Protection Clause, if race was the dominant factor in drawing a map, the state has to show a compelling reason and prove the map is narrowly tailored. Section 2 of the Voting Rights Act adds a separate rule against maps that deny or reduce voting rights based on race, color, or language-minority status. In some cases the VRA actually requires states to draw majority-minority districts to prevent vote dilution, which can create tension with the equal protection standard when race becomes too dominant.11Library of Congress. Racial Vote Dilution and Racial Gerrymandering
Partisan gerrymandering is another matter. In Rucho v. Common Cause (2019), the Supreme Court held that partisan gerrymandering claims are “political questions beyond the reach of the federal courts.”12Cornell Law School Legal Information Institute (LII). Partisan Gerrymandering The Court said extreme partisan maps may be “incompatible with democratic principles” but found no workable judicial standard to separate permissible partisanship from unconstitutional excess. Some state supreme courts have since stepped in under their own constitutions. Pennsylvania’s Supreme Court, for instance, struck down a congressional map under the state’s Free and Equal Elections Clause, a provision with no federal equivalent.
D.C. and the Territories
The 435 voting seats belong exclusively to the 50 states. The District of Columbia and five U.S. territories — Puerto Rico, Guam, American Samoa, the U.S. Virgin Islands, and the Northern Mariana Islands — send non-voting delegates to the House. Puerto Rico’s is called the Resident Commissioner and serves a four-year term; the others serve two years. Delegates can introduce bills, sit on committees, and speak on the floor, but they cannot vote on final passage. Territorial residents are U.S. citizens (or, in American Samoa, U.S. nationals) without voting representation in Congress. These delegate seats are not congressional districts in the sense this article uses the term.
How to Find Your Congressional District
The simplest way to identify your district is the lookup tool on the U.S. House website. Enter your ZIP code and it matches you to a district and a current representative.13house.gov. Find Your Representative Some ZIP codes straddle district lines, so the tool may ask for a street address to pin down the exact match.14house.gov. Find Your Representative
Your state election office or secretary of state website is a good second option, especially right after redistricting when maps have just changed. Boundaries shift after every census, and mid-decade court orders or ballot measures can redraw them in between.8United States Census Bureau. About Congressional Districts You can end up with a new district and a new representative without moving, so it’s worth checking before any federal election.