The 91st United States Congress was a meeting of the legislative branch of the United States federal government, composed of the United States Senate and the United States House of Representatives. It met in Washington, DC from January 3, 1969, to January 3, 1971, during the final weeks of the presidency of Lyndon Johnson and the first two years of the first presidency of Richard Nixon. The apportionment of seats in this House of Representatives was based on the Eighteenth Census of the United States in 1960.