In July 1973, Alexander Butterfield, President Nixon's appointments secretary, testified that Nixon had taped conversations and telephone calls in his offices since 1971. Nixon refused to hand over the tapes to the House Judiciary Committee.
The US Supreme Court rejected Nixon's claims of Executive privilege and ruled that he must turn over the tape recordings of 64 White House conversations to the Committee. Later that month, the Committee passed the first of three articles of impeachment, and on August 8, 1974, Nixon became the first American president ever to resign.
His successor, Vice-President Gerald R Ford, later pardoned Nixon of charges related to the Watergate case.
One of the most famous photographs from the 1970s: President Nixon says goodbye outside the White House, August 9, 1974 as he prepares to board a helicopter for a flight to the Andrews Air Force Base, en route to his ranch in California.
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Photographs: AP Photo/Bob Daughtery