The first Congress (1789-91) had 65 House members, the number provided for in the Constitution until the first census could be held. Based on an estimated population for the 13 states of 3.7 million, there was one representative for every 57,169 people. (At the time, Kentucky was part of Virginia, Maine was part of Massachusetts, and Tennessee was part of North Carolina. Vermont governed itself as an independent republic, despite territorial claims by New York.)
By the time the first apportionment bill took effect in March 1793, Vermont and Kentucky already had joined the Union; the 15 states had a total population of 3.89 million. Since the apportionment law provided for 105 House members, there was one representative for every 37,081 people. (According to the Constitution at the time, only three-fifths of the nation’s 694,280 slaves were counted for apportionment purposes; using that method, the ratio was approximately one representative for every 34,436.)
For more than a century thereafter, as the U.S. population grew and new states were admitted, the House’s membership grew too (except for two short-lived contractions in the mid-1800s). The expansion generally was managed in such a way that, even as the representation ratio steadily rose, states seldom lost seats from one apportionment to the next.
That process ran aground in the 1920s. The 1920 census revealed a “major and continuing shift” of the U.S. population from rural to urban areas; when the time came to reapportion the House, as a Census Bureau summary puts it, rural representatives “worked to derail the process, fearful of losing political power to the cities.” In fact, the House wasn’t reapportioned until after the 1930 census; the 1929 law authorizing that census also capped the size of the House at 435. And there it has remained, except for a brief period from 1959 to 1963 when the chamber temporarily added two members to represent the newly admitted states of Alaska and Hawaii.
There have been occasional proposals to add more seats to the House to reflect population growth. One is the so-called “Wyoming Rule,” which would make the population of the smallest state (currently Wyoming) the basis for the representation ratio. Depending on which variant of that rule were adopted, the House would have had 545 to 547 members following the 2010 census.