The following information from the Congressional Research Service was published Feb. 25, 2021.


Congressional redistricting involves creating geographic boundaries for U.S. House districts within a state. Following each decennial census, House districts are first allocated among states through apportionment (or reapportionment), then allocated within states based upon each state’s redistricting process.

The sections below describe selected federal and state redistricting criteria for congressional districts, followed by a brief discussion of recent related congressional proposals. This product does not provide a legal analysis; for discussion of redistricting law, see CRS Report R44199, Congressional Redistricting: Legal and Constitutional Issues, by L. Paige Whitaker, and CRS Report R44798, Congressional Redistricting Law: Background and Recent Court Rulings, by L. Paige Whitaker.

Selected Redistricting Criteria

Redistricting criteria commonly reflect a combination of state and federal statutes, judicial interpretations, and historical practices. They may be viewed as efforts to provide fair representation for residents and prevent arbitrary or discriminatory boundaries. Certain federal standards apply to House districts, related to population equality and minority protections, but other standards are largely determined by states. Redistricting processes can require or prohibit consideration of certain factors when drawing districts. Often, decisionmakers weigh trade-offs between criteria, and some states specify a priority order in which factors are considered.

Population Equality

Federal standards address population equality among a state’s congressional districts. The U.S. Supreme Court has addressed population size variance among congressional districts within a state, or malapportionment. Under the “equality standard” or “one person, one vote” principle, the Court has found congressional districts within a state should be drawn to approximately equal population sizes. Across states, however, district population sizes can vary.

Racial and Language Minority Protections

Another federal requirement comes from Section 2 of the Voting Rights Act (VRA), as amended, which prohibits states or political subdivisions from imposing any voting qualification, practice, or procedure that results in denial or abridgement of the right to vote based on race, color, or membership in a language minority. Under the VRA, states cannot draw district maps that have the effect of reducing, or diluting, minority voting strength.

Compactness and Contiguity

Compactness and contiguity are both related to a district’s shape. A compact district represents a geographically consolidated area. Twenty-nine states require compact congressional districts, but often, state laws do not specify precise measures of compactness. Typically, a compact district would tend to have fairly smooth boundaries or resemble a standard geometric shape; it might have an identifiable “center” reasonably equidistant from any of its boundaries.

A district is generally thought to be contiguous if it is possible to travel between any two points in a district without crossing into a different district. For congressional districts, 33 states require contiguity.

Political Subdivisions and Communities of Interest

Thirty states require consideration of existing political subdivisions (e.g., towns, cities, or counties). Often, it may not be possible to draw districts that are perfectly aligned with other political boundaries, given other redistricting standards, like population equality, that could take precedence.

People within a community of interest generally share a background or characteristics that may be relevant to their legislative representation (e.g., a social, cultural, historical, racial, ethnic, partisan, or economic identity). Twenty-one states require preserving communities of interest. Sometimes, these communities are naturally preserved by following other criteria, such as compactness, or observing political subdivisions.

Political Competition or Considering Existing District/Incumbent

Some states include measures prohibiting districts intended to unduly favor or disfavor a candidate or political party. Gerrymandering is a term often used for the process of drawing districts to benefit a particular party. Traditionally, redistricting has been viewed as an inherently political process, where authorities have used partisan considerations in determining boundaries. Generally, districts today may be drawn in a way that advantages certain candidates or parties, unless prohibited by state constitutional provisions or statutes. Some states expressly allow the use or consideration of party identification information in the redistricting process, whereas others prohibit it. Similarly, some states allow for practices to protect an incumbent or maintain an existing district’s “core,” whereas other states prohibit any practices that favor or disfavor an incumbent or candidate.

Congress and Redistricting Criteria

Aside from requirements established under the VRA, current federal statute generally does not address redistricting standards. During the 19th and early 20th centuries, Congress sometimes required states to follow certain redistricting criteria, as specified in decennial legislation that applied to a particular apportionment and redistricting cycle. Decennial apportionment acts between 1842 and 1911, for example, required districts of “contiguous territory”; acts between 1872 and 1911 required districts with “as nearly as practicable an equal number of inhabitants.” Given the limited role the federal government Congressional Research Service 3 IN11618 · VERSION 2 · NEW has played, overall, in redistricting processes, federalism concerns may arise in the context of certain congressional efforts regarding redistricting.

Some recent congressional proposals would require that states utilize certain criteria (such as population equality, compactness, contiguity, or preservation of political subdivisions) when drawing congressional district boundaries. Bills from the 117th Congress to date that would require specific redistricting criteria include H.R. 1 and H.R. 80; proposals from the 116th Congress included H.R. 1/S. 949, H.R. 124, H.R. 130, H.R. 163, H.R. 1612, H.R. 4000, H.R. 3572/S. 2226, and S. 1972. Often, these district criteria provisions have been included alongside other redistricting measures, such as requiring states to use redistricting commissions or maintain certain standards of public input and transparency throughout the process.

The use of similar redistricting standards over time and across numerous states may indicate a sense among many lawmakers and members of the public that certain representational principles should be embedded in the redistricting process. Applying these principles in practice may not be straightforward, particularly since decisionmakers often must use multiple criteria when creating districts.

Mapmaking software can design districts with the highest levels of geographic and demographic precision, yet technology has not provided a definitive answer to the recurrent question of how districts ought to be drawn. Following the 2010 census, for example, a number of states faced legal challenges regarding congressional redistricting, indicating the persistence of differing perspectives on fairness, representational access, and how to balance competing redistricting criteria. — Sarah J. Eckman, Analyst in American National Government.

This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff to congressional committees and Members of Congress. It operates solely at the behest of and under the direction of Congress. Information in a CRS Report should not be relied upon for purposes other than public understanding of information that has been provided by CRS to Members of Congress in connection with CRS’s institutional role. CRS Reports, as a work of the United States Government, are not subject to copyright protection in the United States. Any CRS Report may be reproduced and distributed in its entirety without permission from CRS. However, as a CRS Report may include copyrighted images or material from a third party, you may need to obtain the permission of the copyright holder if you wish to copy or otherwise use copyrighted material.

Related Posts