Glenn, here in a family photo at 4 months old, was born July 18, 1921, in Cambridge, Ohio.
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During World War II, Glenn enlisted in the Naval Aviation Cadet Program in 1942 and became a pilot for the US Marines a year later. Glenn, pictured here in the cockpit of an F-8 fighter, completed nearly 150 combat missions in World War II and the Korean War.
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In 1957, Glenn, then a Marine major, set the transcontinental air speed record, flying a Vought F-8 Crusader from Los Angeles to New York in three hours and 23 minutes. He became known as one of the top test pilots in the United States and a natural candidate for the emerging space program.
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Glenn's family -- wife Annie, daughter, Carolyn "Lyn" and son David -- greet him at Floyd Bennett Field in New York after his record-breaking transcontinental flight.
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Glenn and his wife, Annie, sandwich their daughter, Carolyn "Lyn," as they embrace following a ceremony honoring his feat. Son David is at left.
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Glenn receives a Distinguished Flying Cross from then-Navy Secretary Thomas Gates at the Pentagon.
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In 1959, NASA selected seven men -- from left, Wally Schirra, Alan Shepard, Gus Grissom, Deke Slayton, Glenn, Scott Carpenter and Gordon Cooper -- as the first US astronauts, known as the Mercury 7.
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Glenn, now a Project Mercury astronaut, is seen through fisheye lens during training in a mock-up of a space capsule.
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Glenn, third from left, and the six other Mercury 7 astronauts participate in US Air Force survival training exercises in 1960 in Nevada. The training was intended to prepare the astronauts in case of an emergency or faulty landing in a remote area.
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The astronauts instantly became national heroes and media sensations. Decades later they were immortalized in the Tom Wolfe best-seller "The Right Stuff" and subsequent film.
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Glenn prepares for the Mercury-Atlas 6 flight. He would becomes the third American in space.
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Glenn inspects artwork to be painted on the outside of his Mercury spacecraft, which he nicknamed Friendship 7. On February 20, 1962, Glenn became the first American to orbit the Earth. After orbiting the Earth three times in four hours and 55 minutes, the Friendship 7 landed in the Atlantic Ocean.
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Following his Mercury flight, Glenn and his wife, Annie, join Vice President Lyndon Johnson in the front car of a New York motorcade parade honoring the astronaut. An estimated 4 million people turned out for the March 1, 1962, ticker-tape parade.
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The famed astronaut addresses a joint session of Congress on February 28, 1962.
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Glenn holds his discharge papers after he retired from the Marine Corps and resigned from NASA's astronaut program. Now a national figure, he went on to become an executive for the Royal Crown Cola Co. He would soon explore a career in politics.
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Glenn and his family celebrate his November 1974 election win as US senator from Ohio. He began a 24-year career on Capitol Hill and was widely regarded as an effective legislator and moderate Democrat. He unsuccessfully sought the Democratic presidential nomination in 1984.
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On October 29, 1998, Glenn, then 77, became the oldest person to venture into space. Here, he has his flight suit checked before climbing into the space shuttle Discovery. His second flight into space came 36 years after his legendary Mercury launch.
Glenn joins former President Bill Clinton in Marion, Ohio, during a campaign stop for Hillary Clinton during her 2008 presidential campaign
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Glenn displays his Congressional Gold Medal with Sens. Harry Reid, left, Bill Nelson, second from right, and Mitch McConnell during a ceremony in the Capitol Rotunda in November 2011.
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President Barack Obama presents Glenn with the Presidential Medal of Freedom during a May 2012 ceremony at the White House.