The Apportionment Act of 1911 was the federal law that first capped the U.S. House of Representatives at a fixed size, setting the number at 433 seats and building in a provision that raised the total to 435 when Arizona and New Mexico became states in 1912. Before this law, Congress had almost always enlarged the House after each census so that no state would lose seats. The 1911 Act broke that habit, and the 435-member ceiling it produced has governed every reapportionment since.
What the 1911 Act Did
President William Howard Taft signed the Act on August 8, 1911. The statute set the House at 433 members and distributed those seats among the existing states using the 1910 Census. Section 2 added a contingency: if Arizona and New Mexico achieved statehood before the next census, each would get one additional seat on top of the 433 baseline.1GovTrack. 37 Stat 13 – An Act For the Apportionment of Representatives in Congress Among the Several States Under the Thirteenth Census Both territories were admitted in 1912, and the House has stood at 435 members ever since.
At the ratios in place after the 1910 Census, 435 seats meant roughly one representative for every 210,000 people.2U.S. Census Bureau. Apportionment of Seats in the US House of Representatives That ratio has changed enormously in the years since. The number 435 has not.
The Constitutional Room Congress Was Working In
Article I, Section 2 requires that representatives be divided among the states by population, with an “actual Enumeration” every ten years. It imposes only two hard limits: every state gets at least one representative, and the total cannot exceed one member for every 30,000 people.3Cornell Law – Legal Information Institute. Enumeration Clause and Apportioning Seats in the House of Representatives
By 2020, the U.S. population had passed 330 million, meaning the Constitution would technically allow a House of more than 11,000 members. The ceiling has never come close to binding; the one-per-state floor is the rule that matters. Because no constitutional provision fixes the House at any particular size, Congress has always been free to change that number by ordinary legislation.
Why Congress Stopped Growing the House
From the First Congress on, the House had expanded after almost every decennial census. The only prior contraction came after the 1840 Census, when the total dropped from 242 to 232.4Congressional Research Service. Size of the US House of Representatives Every other reapportionment before 1911 pushed the number higher, because expansion was the easiest way to avoid stripping any sitting member of a seat.
By the early 1900s, membership had reached 391, and a further increase after the 1910 Census would have added more. Floor debates were harder to manage, committees were multiplying, and coordination in a chamber that size was becoming a serious concern. The 1910 Census pushed Congress to choose between yet another expansion and something different.
Representative Edgar Crumpacker of Indiana, who chaired the House Committee on the Census, framed the tradeoff on the other side. He warned that making districts too large would weaken the tie between voters and their representatives, saying that “the personal interest of the voter in his representative becomes less important to him, and we may lose something of the vital strength of our representative form of government.”5Office of the Historian, U.S. House of Representatives. The 1911 House Reapportionment Congress passed the cap anyway.
The Method of Major Fractions
A fixed House needs a formula. The 1911 Act used the Method of Major Fractions, sometimes called Webster’s Method. Each state’s population is divided by a common divisor to produce a quota, and the quota is rounded using ordinary arithmetic: 0.5 and above rounds up, anything lower rounds down.6EveryCRSReport.com. The House of Representatives Apportionment Formula
The goal was to keep district sizes as close to equal as possible across the states. An earlier approach, Hamilton’s Method, had assigned leftover seats by largest fractional remainder, which could produce a strange result where adding a seat to the House caused a state to lose one. Webster’s fixed rounding point avoided that outcome. This formula governed apportionment from 1911 through the 1930 Census.
What the Act Left Unfinished
The 1911 Act locked in the size of the House but did not create an automatic process for reapportioning the seats after each future census. Congress still had to pass new legislation every ten years to redistribute the 435 seats.
That gap turned into a decade-long failure. The 1920 Census showed, for the first time, that more Americans lived in urban areas than rural ones. Reapportioning the House would have moved seats from rural and Southern states toward Northern cities. Members from districts poised to lose power blocked every reapportionment bill. Legitimate policy disagreements mixed with anxiety about immigration, resistance to the political power of industrial workers, and opposition to counting growing Black populations in Northern cities. No reapportionment bill passed the entire decade, and the 1910 distribution stayed frozen through the 1920s.5Office of the Historian, U.S. House of Representatives. The 1911 House Reapportionment
Congress finally closed the gap with the Reapportionment Act of 1929, sometimes called the Permanent Apportionment Act. That law made reapportionment self-executing. The President transmits the census results and the resulting seat allocation to Congress, and the Clerk of the House sends each state a certificate showing its new number of representatives.7Office of the Law Revision Counsel. 2 USC 2a – Reapportionment of Representatives Unless Congress passes a new law changing the process, reapportionment now happens automatically based on “the then existing number of Representatives,” which has been 435 since 1911.
The Formula Change in 1941
The Major Fractions Method did not last. In 1941, Congress adopted the Method of Equal Proportions, also known as the Huntington-Hill Method, and codified it at 2 U.S.C. § 2b.8Office of the Law Revision Counsel. 2 USC 2b – Method of Equal Proportions This is the formula still in use.
The change came after a National Academy of Sciences review concluded that Equal Proportions did a better job minimizing percentage differences in district population across the states. The two methods differ mainly in where they place the rounding threshold: Webster’s rounds at 0.5, while Huntington-Hill rounds at the geometric mean of two consecutive whole numbers, which is slightly below 0.5 for small numbers and gives less populous states a small edge near the borderline. For larger delegations the difference rarely matters. The 435-seat total from the 1911 Act carried over unchanged.
What the 435 Cap Means Today
With a fixed House and a growing population, districts have kept getting larger. In 1910, each representative served about 210,000 constituents. By 2020, that number had risen to about 761,000.2U.S. Census Bureau. Apportionment of Seats in the US House of Representatives Intermediate points along the way: roughly 280,700 per seat in 1930, 410,500 in 1960, and 572,500 in 1990.
Those national averages hide sharp inequality between states. After the 2020 Census, the most populous district was nearly twice the size of the least populous. The one-seat constitutional floor is the reason: a small state like Wyoming, with about 577,000 people, gets the same single seat as a state with almost twice that population. As the average district grows, so does the gap between the smallest and largest.
Can the Cap Be Changed?
The 435 number is a statute, not a constitutional command. Congress can change it with an ordinary law. Legal challenges to the cap have failed. In Clemons v. U.S. Department of Commerce (2010), plaintiffs argued that the widening population gap between the largest and smallest districts violated one-person, one-vote. The Supreme Court dismissed the case for lack of jurisdiction without reaching the merits. No court has struck down the 435 cap, and the prevailing view is that Congress has broad discretion to set the House anywhere between the constitutional floor and ceiling.9Visit the Capitol. How Your State Gets Its Seats Congressional Apportionment
The most discussed expansion proposal is the Wyoming Rule, which would set each district’s target population equal to that of the least populous state. Applied to 2020 Census figures, it would produce a House of 574 seats; applied to 2010 figures, it would have produced 543. Supporters argue a larger House would shrink the gap between districts and bring members closer to their constituents. Opponents point to the logistical problems that pushed Congress to cap the House in the first place. No such proposal has moved past the committee stage, and the number Congress settled on in 1911 remains the law.