Apportionment is the process of dividing the 435 memberships, or seats, in the House of Representatives among the 50 states. At the conclusion of each decennial census, the results are used to calculate the number of House memberships to which each state is entitled. These maps show the changes to the number of Congressional seats for each state between apportionment based on the 1990 Census and apportionment based on the 2000 Census.