Apropos of a major project I'm working on: Up through 1920, Congress passed an apportionment act every 10 years. They regularly increased the size of the House, and specified how districts had to look, e.g., from 1870-1930 they had to have a roughly even number of residents. 1/ https://twitter.com/davegengler/status/1307733898592489472

had to be compact, etc. If you look at the appendices to Colgrove v. Green and Baker v. Carr, the "roughly even" requirement actually worked pretty well. Then, in 1920, the headline for the census was "for the 1st time, a majority of Americans lived in urban areas." 2/

Now by "urban" it mean "in excess of 5k people" but nevertheless, rural legislators freaked out, especially Midwestern Republicans who had seen major Democratic cities spring up practically overnight in Illinois, Michigan, Ohio, etc. 3/

So they didn't re-apportion in 1920. At all. Obviously this was controversial, given the Constitution and whatnot, so in 1929 they came up with a compromise: They would re-apportion, but they would do away with the equality requirement. 4/

So states like IL would add seats, but they would make them "at-large" seats so that they didn't have to disturb the underlying map that had been put in place. They also made re-apportionment automatic so that a deadlock like 1920 wouldn't happen, and set the House at 435. 5/

Incidentally, this is what set the stage for one-person-one-vote. In 1946 the Court refused to strike down Illinois' map, even though one IL district had 112k members, while another had 914k. 6/

The Court finally had enough in 1963 in Wesberry, and struck down a Georgia map with 823k in the Atlanta district but 272k in the rural 9th district. 7/7