Finally, Aldrin called out, "Contact light" -- a signal that a five-foot-long metal probe, protruding from Eagle's landing legs, had touched the surface. The ship gently settled. Finally, Armstrong came on the radio.
"Houston, Tranquility Base here, the Eagle has landed."
Armstrong would say later that he considered the landing a much greater challenge, and a greater accomplishment, than actually walking on the surface. But after making sure Eagle was in good shape for the return trip, he and Aldrin put on their bulky backpacks and prepared to open the hatch.
It was 10:56 p.m., Eastern Daylight Time, when Armstrong backed down the ladder of the Lunar Module, went back up a step to make sure he could, and then planted his left boot in the lunar soil.
Armstrong walked on the moon for two hours and 21 minutes, Aldrin for about half an hour less. They took rock samples, set up two experiments, and took a phone call from President Nixon. They planted an American flag (with some difficulty; its staff wouldn't stand firmly in the lunar dirt and the flag itself, stiffened with wires, rumpled). They bounded around in the weak lunar gravity, reporting it was great fun but a little hard to stop.
Armstrong carried a camera, mounted on the chest of his spacesuit, and took some of the most famous pictures of the century. Aldrin did not have a camera -- so, in one of the ironies of the space age, almost all the still pictures from the Apollo 11 moonwalk are by Armstrong, not of him.
After a fitful night's sleep, the two men lifted off from the lunar surface and rejoined Collins in Columbia. They splashed down safely in the Pacific on July 24, 1969. They were greeted by ticker-tape parades and a beaming President Nixon. After that, Armstrong tried his best to resume a private life.
He served for a few years as a NASA manager in Washington. He taught engineering at the University of Cincinnati, not far from his birthplace. He served on corporate boards. He was appointed to the panels that investigated the Apollo 13 accident and the Challenger disaster. He declined almost all requests for interviews, and stopped giving autographs when people sold them for thousands of dollars.
A few personal details emerged: He suffered a minor heart attack in 1991. His wife Jan divorced him in 1994 and he soon married Carol Knight. In 2005 his authorized biographer, James R. Hansen, wrote, "Neil Armstrong today seems to be a very happy man -- perhaps happier than at any other time in his life."
Armstrong, who was born in the small town of Wapakoneta, Ohio, on Aug. 5, 1930, said he did not want to be an icon, remembered only for that one-week trip he made in 1969. He did appear at the White House to mark major anniversaries of Apollo 11, and when he did he urged America to go on exploring.
"There are great ideas undiscovered, breakthroughs available to those who can remove one of truth's protective layers," he said in 1994. "There are places to go beyond belief."
Editor's Note: This article was written and published on Aug. 25, 2012, the day Neil Armstrong died, and was updated this week with a new video to commemorate the anniversary of Armstrong's death. This update changed the time stamp on our mobile site, causing some to share the story on social media thinking we had published news of Armstrong's death today. We regret the confusion caused by the updated time stamp.