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If we were to pick a year that marked the total demise of representative government and the entrenchment of a two party oligarchy in the United States, then 1921 would be that year. Congress, dominated by rural politicians who stood to lose clout in a quickly urbanizing nation, failed to reapportion the House following the 1920 census. And having gotten away with acting unconstitutionally, the Congress compounded the crime in The Reapportionment Act of 1929, such that apportionment of 435 seats would occur automatically following each decennial census. See page 26, section 22 of this PDF