The 435 seats in the U.S. House are divided among the states by population, and each state is split into congressional districts. Where those district lines fall shapes representation for years.
Apportionment
Every ten years the U.S. Census counts the population, and the 435 House seats are reapportioned among the states. States that grow faster gain seats; slower-growing states can lose them. Every state keeps at least one seat.
Redistricting
After reapportionment, each state redraws its district boundaries. Depending on the state, this is done by the legislature or by an independent commission. This is also where gerrymandering can occur.
One person, one vote
Congressional districts within a state must have roughly equal populations, so each representative speaks for a similar number of people. That's why districts are redrawn as populations shift.
Finding your district
Your congressional district is based on your home address. You can look it up through your state or county election office, and it determines which U.S. House candidates appear on your ballot.
Frequently asked questions
How often are districts redrawn?
Typically once a decade, after the census, though court rulings can force mid-decade changes.
Why do districts have odd shapes?
Sometimes geography or communities of interest; sometimes deliberate line-drawing to favor a party — gerrymandering.