He was still a force at NASA, though, and kept lobbying for another flight. Finally, in 1969, after going in secret for corrective surgery, he was put back on active status -- and quickly assigned himself to command an Apollo moon flight. In 1971, on Apollo 14, he became the fifth man to walk on the Moon.
Years later he was asked what he thought his greatest accomplishment had been, and he said being chosen above the other Mercury astronauts to fly Freedom 7. Then he paused.
"I must admit," he said, "maybe I am a piece of history after all."