NASA
On April 9, 1959, NASA introduced its first astronaut class, the Mercury 7. Front row, left to right: Walter M. Schirra, Jr., Donald K. "Deke" Slayton, John H. Glenn, Jr., and M. Scott Carpenter; back row, Alan B. Shepard, Jr., Virgil I. "Gus" Grissom, and L. Gordon Cooper, Jr.
John Glenn is the only living member of the original seven, which included Alan Shepard, Scott Carpenter, Wally Schirra, Gus Grissom, Deke Slayton, and Gordon Cooper.
The Mercury 7 were not just average American men. They were all military test pilots, but also college-educated as engineers and in excellent physical condition.
Each man emerged from one of the world's most competitive selection processes that included a daunting combination of interviews, written exams, mental evaluations, and stress tests.
What followed were two years of intensive training before risking everything to become the first Americans to rocket into space.