The U.S. Postal Service unveiled the stamp at the Rocket Garden of the Kennedy Space Center Visitor Complex in Cape Canaveral, Fla., in a ceremony attended by fellow Mercury Seven astronaut Scott Carpenter and NASA Administrator Charles Bolden.
Shepard's 15-minute flight on May 5, 1961, took him 116 miles above the Earth and 303 miles from the launch pad. But he did not reach orbit, as Soviet cosmonaut Yuri Gagarin had done three weeks earlier and John Glenn did nine months later.
"He was significant symbolically more than anything else," Roger Launius, a historian at the National Air and Space Museum, told Gannett's Washington news bureau. "In the context of this Cold War rivalry, it was really significant."
In 1971, Shepard commanded Apollo 14, which collected 93 pounds of moon rocks and conducted seismic studies, and he famously hit a golf ball on the moon.
Shepard died in 1998.