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. He commanded the Gemini 8 mission in 1966, bringing back the capsule back in an emergency landing in the Pacific Ocean when a wildly firing thruster kicked it out of orbit.
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.
In 2000, when he agreed to announce the top 20 engineering achievements of the 20th Century as voted by the National Academy of Engineering, Armstrong mentioned one disappointment relating to his moonwalk.
"I can honestly say — and it's a big surprise to me — that I have never had a dream about being on the moon," he said.
From 1982 to 1992, Armstrong was chairman of Charlottesville, Va.-based Computing Technologies for Aviation Inc., a company that supplies computer information management systems for business aircraft.
He then became chairman of AIL Systems Inc., an electronic systems company in Deer Park, N.Y.
Armstrong married Carol Knight in 1999, and the couple lived in Indian Hill, a Cincinnati suburb. He had two adult sons from a previous marriage.
Armstrong's is the second death in a month of one of NASA's most visible, history-making astronauts. Sally Ride, the first American woman in space, died of pancreatic cancer on July 23 at age 61.
Just prior to the 50th anniversary of Glenn's orbital flight this past February, Armstrong offered high praise to the elder astronaut. Noted Armstrong in an email: "I am hoping I will be 'in his shoes' and have as much success in longevity as he has demonstrated." Glenn is 91.