November 1974-1999 - Elected to the U.S. Senate and serves four consecutive terms (D-Ohio).
1978 - Chief author of the Nuclear Nonproliferation Act of 1978, prohibiting the sale of nuclear equipment to nations that currently have none.
1983-1984 - Runs unsuccessfully for the Democratic presidential nomination for the 1984 election. He drops out of the race after failing to win any early primaries or caucuses.
1987-1995 - Glenn is chairman of the Senate Governmental Affairs Committee, and sits on the Foreign Relations, Armed Services Committees and the Special Committee on Aging.
February 20, 1997 - Glenn announces on the 35th anniversary of his orbit around the earth that he will not run for re-election in the U.S. Senate.
1998 - NASA invites him to rejoin the space program as a member of the Space Shuttle Discovery Crew. Glenn serves as Payload Specialist 2 in the STS-95 crew aboard the Space Shuttle Discovery.
October 29, 1998 - A 77-year-old Glenn becomes the oldest person ever to venture into space.
February 2006 - NASA awards Glenn and 37 other astronauts the Ambassador of Exploration Award.
November 16, 2011 - Receives the Congressional Gold Medal for Distinguished Astronauts along with Neil Armstrong, Buzz Aldrin and Michael Collins.
May 29, 2012 - Receives the Presidential Medal of Freedom from President Barack Obama during an East Room White House ceremony.