"The fact that we were able to see it and be a part of it means that we are in our own way witnesses to history," he said.
The 1969 landing met an audacious deadline that President Kennedy had set in May 1961, shortly after Alan Shepard became the first American in space with a 15-minute suborbital flight. (Soviet cosmonaut Yuri A. Gagarin had orbited the Earth and beaten the U.S. into space the previous month.)
"I believe this nation should commit itself to achieving the goal, before the decade is out, of landing a man on the moon and returning him safely to Earth," Kennedy had said. "No single space project in this period will be more impressive to mankind, or more important to the long-range exploration of space; and none will be so difficult or expensive to accomplish."
The end-of-decade goal was met with more than five months to spare. "Houston: Tranquility Base here," Armstrong radioed after the spacecraft settled onto the moon. "The Eagle has landed."
"Roger, Tranquility," the Houston staffer radioed back. "We copy you on the ground. You've got a bunch of guys about to turn blue. We're breathing again. Thanks a lot."
The third astronaut on the mission, Michael Collins, circled the moon in the mother ship Columbia 60 miles overhead while Armstrong and Aldrin went to the moon's surface.
In all, 12 American astronauts walked on the moon between 1969 and the last moon mission in 1972.
For Americans, reaching the moon provided uplift and respite from the Vietnam War, from strife in the Middle East, from the startling news just a few days earlier that a young woman had drowned in a car driven off a wooden bridge on Chappaquiddick Island by Sen. Edward Kennedy. The landing occurred as organizers were gearing up for Woodstock, the legendary three-day rock festival on a farm in the Catskills of New York.
Armstrong was born Aug. 5, 1930, on a farm near Wapakoneta in western Ohio. He took his first airplane ride at age 6 and developed a fascination with aviation that prompted him to build model airplanes and conduct experiments in a homemade wind tunnel.
As a boy, he worked at a pharmacy and took flying lessons. He was licensed to fly at 16, before he got his driver's license.
Armstrong enrolled in Purdue University to study aeronautical engineering but was called to duty with the U.S. Navy in 1949 and flew 78 combat missions in Korea.
After the war, Armstrong finished his degree from Purdue and later earned a master's degree in aerospace engineering from the University of Southern California. He became a test pilot with what evolved into the National Aeronautics and Space Administration, flying more than 200 kinds of aircraft from gliders to jets.
Armstrong was accepted into NASA's second astronaut class in 1962 - the first, including Glenn, was chosen in 1959 - and commanded the Gemini 8 mission in 1966. After the first space docking, he brought the capsule back in an emergency landing in the Pacific Ocean when a wildly firing thruster kicked it out of orbit.
Armstrong was backup commander for the historic Apollo 8 mission at Christmastime in 1968. In that flight, Commander Frank Borman, and Jim Lovell and Bill Anders circled the moon 10 times, and paving the way for the lunar landing seven months later.
Aldrin said he and Armstrong were not prone to free exchanges of sentiment.
"But there was that moment on the moon, a brief moment, in which we sort of looked at each other and slapped each other on the shoulder ... and said, `We made it. Good show,' or something like that," Aldrin said.
An estimated 600 million people - a fifth of the world's population - watched and listened to the landing, the largest audience for any single event in history.
Parents huddled with their children in front of the family television, mesmerized by what they were witnessing. Farmers abandoned their nightly milking duties, and motorists pulled off the highway and checked into motels just to see the moonwalk.
Television-less campers in California ran to their cars to catch the word on the radio. Boy Scouts at a camp in Michigan watched on a generator-powered television supplied by a parent.
Afterward, people walked out of their homes and gazed at the moon, in awe of what they had just seen. Others peeked through telescopes in hopes of spotting the astronauts.
In Wapakoneta, media and souvenir frenzy was swirling around the home of Armstrong's parents.
"You couldn't see the house for the news media," recalled John Zwez, former manager of the Neil Armstrong Air and Space Museum. "People were pulling grass out of their front yard."
Armstrong, Aldrin and Collins were given ticker tape parades in New York, Chicago and Los Angeles and later made a 22-nation world tour. A homecoming in Wapakoneta drew 50,000 people to the city of 9,000.
In 1970, Armstrong was appointed deputy associate administrator for aeronautics at NASA but left the following year to teach aerospace engineering at the University of Cincinnati.
He remained there until 1979 and during that time bought a 310-acre farm near Lebanon, where he raised cattle and corn. He stayed out of public view, accepting few requests for interviews or speeches.