The data collected by the census determine the number of seats each state has in the U.S. House of Representatives (a process called apportionment) and is also used to distribute billions in federal funds to local community. What are Congressional Districts? After the apportionment of congressional seats among the states, which is based on decennial census population counts, each state with multiple seats is responsible for establishing congressional districts for the purpose of electing representatives. Www.census.gov