A very odd historical episode I learned about only from reading Daniel Okrent’s Last Call: The Rise and Fall of Prohibition is the congressional reapportionment following the 1920 census. Or, rather, the lack of reapportionment. They just didn’t do one, part of an effort to dilute the franchise of Catholic and Jewish immigrants.
One consequence of this is that I’d never understood before is that the Roosevelt Revolution of the early 1930s was powered by what must have been an incredibly dramatic redrawing of the electoral map. Consider that in 1910 the US population was 92 million and by the time they redistricted 20 years later it had grown to 122 million. And the change wasn’t even distributed. Kansas went from 1.69 million to 1.88 million (11% increase) while Chicago went from 2.19 million to 3.38 million (54% increase). Redistricting is always important, but when you manage to skip a decade the results get really wild.