The U.S. House of Representatives has been a popularly-elected body with its membership reconstituted every two years throughout its history. The biennial term was a compromise at the Federal Constitutional Convention, but there have been efforts as late as the 1960s to change its length. The two-year term has dictated the rhythm of legislative business in the House.
https://history.house.gov/Institution/Origins-Development/Biennial-Elections/
