Astronaut Gus Grissom climbs into "Liberty Bell 7" spacecraft before launch on the morning of July 21, 1961. Astronaut John Glenn, Grissom's back up, helps him into the capsule.
A problem with the hatch led Grissom's capsule to sink after splashdown. It was salvaged from the Atlantic Ocean in 1999.
Grissom's suborbital flight on a Mercury-Redstone rocket was the second manned U.S. spaceflight. Glenn followed him a month later with the first orbital flight by an American.
Source: NASA