Final answer:
The number of seats in the House of Representatives has been fixed at 435 since the Permanent Apportionment Act of 1929, with seats reapportioned among states every ten years based on census data.
Step-by-step explanation:
The number of seats in the House of Representatives has been fixed at 435 since 1929. This permanent cap was established by the Permanent Apportionment Act of 1929 following a period of growth when the number of House members continued to increase with the population. The Act was a response to concerns about the physical space limitations within the Capitol and the inefficiency that might result from a legislative body that was too large.
Since then, even as the population of the United States has grown significantly, the number of seats has remained unchanged, with reapportionment of the seats among the states occurring every ten years based on the census data to ensure proportional representation.