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, D.C., 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 1960 United States census. Both chambers had a Democratic majority - albeit with losing their supermajority status in the Senate. With Richard Nixon being sworn in as president on January 20, 1969, this ended the Democrats' overall federal government trifecta that they had held since the 87th Congress. Major events January 20, 1969: Richard M. Nixon became 37th President of the United States. Major legislation December 30, 1969: Tax Reform Act of 1969, December 30, 1969: Federal Coal Mine Health and Safety Act, January 1, 1970: National Environmental Policy Act, April 1, 1970: Public Health Cigarette Smoking Act, April 3, 1970: Environmental Quality Improvement Act, May 21, 1970: Airport and Airway Development Act, , title I August 12, 1970: Postal Reorganization Act (United States Postal Service), August 15, 1970: Economic Stabilization Act, Title II of September 22, 1970: District of Columbia Delegate Act, October 15, 1970: Organized Crime Control Act, (including the Racketeer Influenced and Corrupt Organizations Act ("RICO") October 15, 1970: Urban Mass Transportation Act of 1970, October 26, 1970: Bank Secrecy Act, October 26, 1970: Legislative Reorganization Act of 1970 October 27, 1970: Controlled Substances Act, October 30, 1970: Rail Passenger Service Act (Amtrak), December 24, 1970: Family Planning Services and Population Research Act of 1970, December 24, 1970: Plant Variety Protection Act, December 29, 1970: Occupational Safety and Health Act (OSHA), December 31, 1970: Clean Air Act Extension, December 31, 1970: Housing and Urban Development Act of 1970, , including title VII, National Urban Policy and New Community Development Act of 1970 January 12, 1971: Foreign Military Sales Act of 1971, January 13, 1971: Lead-Based Paint Poisoning Prevention Act, Party summary The count below identifies party affiliations at the beginning of the first session of this Congress, and includes members from vacancies and newly admitted states, when they were first seated. Changes resulting from subsequent replacements are shown below in the "Changes in membership" section. Senate House of