In Wesberry v. Sanders the Supreme Court of the United States rules that congressional districts have to be approximately equal in population.

Wesberry v. Sanders, 376 U.S. 1 (1964), was a landmark U.S. Supreme Court case in which the Court ruled that districts in the United States House of Representatives must be approximately equal in population. Along with Baker v. Carr (1962) and Reynolds v. Sims (1964), it was part of a series of Warren Court cases that applied the principle of "one person, one vote" to U.S. legislative bodies.

The Supreme Court of the United States (SCOTUS) is the highest court in the federal judiciary of the United States. It has ultimate appellate jurisdiction over all U.S. federal court cases, and over state court cases that turn on questions of U.S. constitutional or federal law. It also has original jurisdiction over a narrow range of cases, specifically "all Cases affecting Ambassadors, other public Ministers and Consuls, and those in which a State shall be Party." In 1803, the court asserted itself the power of judicial review, the ability to invalidate a statute for violating a provision of the Constitution via the landmark case Marbury v. Madison. It is also able to strike down presidential directives for violating either the Constitution or statutory law.

Congressional districts in the United States are electoral divisions for the purpose of electing members of the United States House of Representatives. The number of voting seats within the House of Representatives is currently set at 435, with each one representing an average of 761,169 people following the 2020 United States census. The number of voting seats has applied since 1913, excluding a temporary increase to 437 after the admissions of Alaska and Hawaii. The total number of state members is capped by the Reapportionment Act of 1929. In addition, each of the five inhabited U.S. territories and the federal district of Washington, D. C., sends a non-voting delegate to the House of Representatives.