United States congressional apportionment

United States congressional apportionment is the process by which seats in the United States House of Representatives are distributed among the 50 states according to the most recent constitutionally mandated decennial census. Each state is apportioned a number of seats which approximately corresponds to its share of the aggregate population of the 50 states. However, every state is constitutionally guaranteed at least one seat.

Because the size of a state's total congressional delegation determines the size of its representation in the U.S. Electoral College, congressional apportionment also affects the U.S. presidential election process as well.

The number of voting seats in the House of Representatives is currently set to 435, and has been since 1913, excluding a temporary increase to 437 after the admissions of Alaska and Hawaii. Though the actual reapportionment will normally occur in respect of a decennial census, the law that governs the total number of representatives and the method of apportionment to be carried into force at that time can be created prior to the census.

The decennial apportionment also determines the size of each state's representation in the U.S. Electoral College. Under Article II, Section 1, Clause 2 of the U.S. Constitution, any state's number of electors equals the size of its total congressional delegation (i.e., House seat(s) plus Senate seats).

Federal law requires the Clerk of the House of Representatives to notify each state government of its entitled number of seats no later than January 25 of the year immediately following the census. After seats have been reapportioned, each state determines the boundaries of congressional districts—geographical areas within the state of approximately equal population—in a process called redistricting. Any citizen of the State can challenge the constitutionality of the redistricting in their US district court.

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