Fifty years ago this summer, three men aboard Apollo 11 traveled from our planet to the Moon. On July 20, 1969, at 10:56:15 p.m. EDT, 38-year-old commander Neil Armstrong moved his left foot from the landing pad of the lunar module (LM) Eagle onto the gray, powdery surface of the Sea of Tranquility and became the first person to step onto the lunar soil. Armstrong declared: "That's one small step for [a] man, one giant leap for mankind." Nineteen minutes later, 39-year-old LM pilot Edwin "Buzz" Aldrin followed Armstrong onto the surface. Fifteen hours later, after spending two and a half hours outside of Eagle, the two men lifted off and returned to their command module (CM) Columbia, manned patiently by the third member of their crew, 38-year-old CM pilot Michael Collins. Four days later, the three men were back home. Although five additional lunar landings would occur, each more challenging and scientifically ambitious than its predecessor, Apollo 11 stands alone as the greatest technological accomplishment of the 20th century. The mission also signaled the beginning of the end of the "Golden Age" of America's space program.