But more than that, it kick-started America's future as a spacefaring nation.
On the 50th anniversary of Shepard's pioneering flight, his three daughters, Laura Churchley, Julie Jenkins and Alice Wackermann, joined former space workers and their families, community leaders and others to celebrate the flight and its legacy.
"In the audience today, we have more than 100 workers from the Mercury era who devoted their lives to flying humans safely in space," said Kennedy Space Center Director Bob Cabana. He asked them to stand, and they were greeted by a round of applause.
"You should be extremely proud of what you did for our country and for humankind," Cabana said.
The flight of "Freedom 7" boosted spirits throughout the country at a time when the U.S. appeared to be faltering in the quest for a viable space program. Just weeks before, on April 12, 1961, Russian cosmonaut Yuri Gagarin had become the first human in space, orbiting the Earth for 108 minutes in the Vostok 1 spacecraft.
A U.S. Navy test pilot, Shepard was one of the first astronauts selected by NASA. The "Mercury Seven" astronauts - M. Scott Carpenter, Leroy Gordon Cooper, Shepard, John H. Glenn Jr., Virgil I. "Gus" Grissom Jr., Walter M. "Wally" Schirra Jr., and Donald K. "Deke" Slayton - were introduced to the nation in April 1959. NASA kept the identity of the first astronaut to fly a secret until word of Shepard's command got out just days before the launch.
After ignition, Shepard reached up to start the mission clock. The vehicle experienced some vibration about a minute and a half into flight when it pierced the area of peak aerodynamic pressure, but Shepard enjoyed a smoother ride as the Redstone pushed skyward. Once the Mercury spacecraft separated from the rocket, the capsule turned, with its heat shield facing forward. During the short flight, Shepard took in the amazing view and experimented with the spacecraft's controls.
At the anniversary event, the entire flight was replayed in a video that began five minutes before launch time, with liftoff and landing at the precise moment when Shepard began and ended his mission 50 years ago.
"It was an intense countdown. Everybody had their job. There was no joking around," said former Chief Test Conductor Bob Moser. "But we enjoyed it, and it worked. Congratulations to all of us. We were a great team."
The flight was significant not only because it displayed bravery and technological progress, but also because it played out before journalists and the public. For the first time, the world was able to share in the tension and excitement as the historic event unfolded on television in real time.
"To me - and I've gone through hundreds of launches and done countdowns in hundreds of launches - the first is always very special," said Jack King, former chief of NASA's Public Information Office. "I must admit, it's the only one when I was misty-eyed. The first American in space! I couldn't be prouder. And I couldn't be prouder for being a part of it."
"Freedom 7" was only the beginning of Shepard's spaceflight career. He went on to serve as chief of the Astronaut Office after his first flight. In 1971, he commanded the Apollo 14 mission, landing along with Lunar Module Pilot Edgar Mitchell in the Fra Mauro region originally intended as Apollo 13's target while Command Module Pilot Stuart Roosa orbited overhead.
"I remember every time he spoke, he always gave credit to everyone in NASA who built the good ships that brought him home to us safely," Churchley said. "We thank you all very much."
Human spaceflight has changed dramatically in the ensuing half-century. A space shuttle flight is typically about two weeks; long-duration increments aboard the massive International Space Station last several months. Today's space missions are intricate and complex, requiring years of training and rehearsal, with crews of five, six or seven astronauts working together on a single flight. Rather than a race to the finish, a spirit of international cooperation provides a backdrop for today's space program.
"It's an honor to share this day with so many people who helped NASA pioneer human spaceflight and enable the agency's many accomplishments throughout our existence," NASA Administrator Charles Bolden said. "I salute all of you."