The House is divided "according to their respective Numbers," counted in a census every ten years (Article I, Section 2). Two steps follow each census: apportionment (how many seats each state gets) and redistricting (where the lines go inside each state).
Why it works
Apportionment is arithmetic, and the House is a fixed pie. The House grew with the country until it reached 435 after the 1910 census (seated in 1913); the Reapportionment Act of 1929 fixed that number by law, and the seats are divided by a formula called the "method of equal proportions." (Alaska and Hawaii briefly raised it to 437 until the 1960 census.) So when one state grows faster than others, another state loses a seat. Redistricting is politics: state legislatures, or in some states independent commissions, draw the lines. Drawing them to help a party or group is called gerrymandering, after Massachusetts Governor Elbridge Gerry, who signed an 1812 map with a district shaped like a salamander.
| Case | Year | Holding |
|---|---|---|
| Baker v. Carr | 1962 | Courts may hear claims that legislative districts are unequal; they are not "political questions" (6–2) |
| Wesberry v. Sanders | 1964 | Congressional districts in a state must be as nearly equal in population as practicable (6–3) |
| Reynolds v. Sims | 1964 | Both houses of a state legislature must have districts of equal population: "one person, one vote" (8–1) |
| Shaw v. Reno | 1993 | District lines drawn mainly on the basis of race face strict scrutiny (5–4) |
| Rucho v. Common Cause | 2019 | Claims of partisan gerrymandering are political questions that federal courts cannot decide (5–4); state courts and laws may still limit it |
Key idea
After each census the 435 seats are apportioned by population (each state gets at least one); states then draw districts, which must be nearly equal in population (Wesberry, 1964), after Baker v. Carr (1962) let courts hear such claims. Drawing lines for advantage is gerrymandering.
Worked example: A fixed pie
After a census, Texas gains two seats. What happens to the size of the House?
- The size is fixed by law at 435.
- So two seats must come from other states that grew more slowly.
Answer: It stays at 435; other states lose seats.
Worked example: Two cases, two levels
A state's congressional districts range from 500,000 to 900,000 people. Which case is the closest precedent, and which clause did it rest on?
- These are districts for the U.S. House, not the state legislature.
- Wesberry v. Sanders (1964) required equal congressional districts, reading Article I, Section 2 ("chosen... by the People").
- Reynolds v. Sims applied the same idea to state legislatures under the Equal Protection Clause.
Answer: Wesberry v. Sanders, under Article I, Section 2.
Common mistake
Thinking the number of House seats grows with each census. It has been 435 since 1913 (by law since 1929), except briefly in 1959–1963. States gain or lose seats as populations shift. Check: a question that adds seats to one state must take them from another.