While Armstrong and fellow astronauts Edwin "Buzz" Aldrin and Michael Collins were changing the course of history in a different part of the galaxy, a select group of well-trained men were doing the best they could to make their mark down among the rivers, mountains, forests and cities of our planet.
Their uniforms didn't have aluminum neck rings and hose fittings, sun-shielded helmets and space boots, though. They wore the traditional caps, numbered jerseys, pants and spikes of Major League Baseball.
Twenty teams were in action on the dirt and grass diamonds of Earth, and many of the players who suited up that day remember it all vividly and with emotion. Here are some of their stories.
Two moonshots in one day
The day man first walked on the moon started like any other game day for Gaylord Perry, a 30-year-old right-hander in the middle of a season for the San Francisco Giants in which he'd go 19-14 with a 2.49 ERA.
But though Perry would eventually qualify for the Hall of Fame as a pitcher, he never quite got his due as a hitter, and that was about to change -- sort of.
First, a flashback to 1964, Perry's third season in the Major Leagues.
As Perry recalls, his manager, Alvin Dark, and a sportswriter for the San Francisco Examiner newspaper, Harry Jupiter, were watching Perry take his hacks during batting practice.
"I was good friends with Harry, and he and Alvin were watching me in the cage, and Harry said something like, 'You know, Perry isn't a bad hitter. He might hit a home run or two for you,' " Perry says.
"Of course, Alvin saw a whole lot that he liked in my pitching and saw a whole lot that he didn't like in my hitting, and he said, 'Mark my words. A man will land on the moon before Gaylord Perry hits a home run.' "
More than five years later, Apollo 11 landed on the dark, cratered lunar surface at 1:17 p.m. PT. Down among the green hills of Earth, a Sunday crowd of 32,560 had settled into their seats at Candlestick Park on the San Francisco Bay to watch their hometown Giants hosting the Los Angeles Dodgers.
And in the bottom of the third inning, a not-at-all-serious prophecy was fulfilled.
"Well, about the top of the third, over the loudspeaker, they were telling everybody to stand and give a moment of silent thanks for the astronauts who landed on the moon," Perry remembers.
"And I'd say 30 minutes later, Claude Osteen grooved me a fastball, and I hit it out of the park."
Perry pitched a complete game and got the victory, one of the 314 he'd notch over a legendary, colorful 22-year career that saw him log more than 5,000 innings, strike out more than 3,500 batters and wear eight uniforms.
His moonshot 40 years ago was the first of six career homers and, as he explains, the thing he's talked the most about to this day. More than the Hall of Fame. More than the 300 club. Heck, even more than the Vaseline.
"I don't mind it at all," he says. "I was very proud, because I remember seeing President Kennedy saying we will put a man on the moon before anybody else. And that was a very proud moment, with the astronauts being safe and being able to get back home, it was an amazing thing.
"It was more of a feat than me hitting a home run."
Two weeks ago, Perry was vacationing at his fishing house on the Outer Banks of North Carolina. He was in the garage looking for something, opened a wooden box and found the bat that launched that historic first homer.
"It made me think about July 20, 1969, all over again, and it brought a big smile to my face," he says. "Hitting a home run that day and winning that day and a man landing on the moon ... That was a great day.
"You can be sure I'll have a glass of champagne [today] and celebrate it all over again."
Once in a Blue moon
About 400 miles south of San Francisco, a launch of a different kind was taking place on July 20, 1969.
There, in Anaheim Stadium, in the first game of a double-header, a hard-throwing 19-year-old Oakland Athletics left-hander from Mansfield, La., by the name of Vida Rochelle Blue toed the rubber in a Major League game for the first time in what would be a storied career.
Blue, eight days shy of his 20th birthday and straight out of Double-A ball, skipping an entire level of the Minor Leagues, says now that he had no doubts when he stepped on that mound.
"Well, I thought I was ready, and the folks that brought me up thought I was ready," says Blue. "So why wouldn't I have thought that way?"
Blue had been following the news stories chronicling the space program, something he still does to this day, having "TiVo'd just about every shuttle launch in the last 10 years," he says.
But as soon as he began warming up that day, throwing to catcher Phil Roof, the significance of the situation hit him with the force of the 100-mph fastballs he threw.
"I was fresh out of the Southern League," he says with a laugh. "The crowd itself was so different. It was the classic deer-in-the-headlights syndrome. As cool and as calm as you think you are, you're really not. You're thrust into a situation you've never experienced before.
"I mean, seriously, before that game, attendance at one of my games might have been 5,000, maybe 10,000. And now it's 35,000. And these were big league hitters. I'd never seen that type of talent before."
Blue would go on to win 209 career games, make six All-Star teams and take the American League Cy Young and Most Valuable Player awards in his watershed season of 1971, when he went 24-8 with a 1.82 ERA, eight shutouts and 301 strikeouts in 312 innings.
But on that day he was a regular 19-year-old kid.
He lasted 5 1/3 innings, giving up five runs -- three earned -- on six hits, including two home runs, in the A's 7-3 loss to the Angels. His career began with an 0-1 record.
"I was a young, cocky kid, and when you're young and cocky, you think you have it all and know it all," Blue says. "I was no different. That was the attitude I had. That's what kids that age do, and I certainly did it."
At some point during the game, Blue remembers, he heard about the moon landing and, for at least a moment, was able to escape the whirlwind of nerves unfolding around him to focus on something bigger than baseball.
Forty years later, Blue says that he's touched to even be asked about that day.
"I just remember it was obviously a great chance for me, and, as it turns out, it was a unique thing to pitch on the day this country landed a man on the moon.
"It's pretty cool and kind of flattering that it happened on the same day."
An amazing night in an Amazin' season
Ron Swoboda recalls July 20, 1969, as clearly as the famous catch he made during the World Series in which he unexpectedly found himself three months later.
The New York Mets outfielder, whose team had just split a doubleheader with the Montreal Expos in Parc Jarry north of the border, hunkered down at the airport, waiting with his teammates for the United Airlines charter back to LaGuardia.
The minutes turned to hours. The players turned antsy. The plane just sat there.
Aware of the historic proceedings taking place, oh, about 240,000 miles from the planet they were on, several Mets summoned thoughts of Armstrong, Aldrin and Collins with verbal jabs at the flight crew.
"I definitely heard at least one or two guys say something like, 'Great, we can make it to the moon, but we can't fly from Montreal to New York,' " Swoboda says with a laugh.
But in a season that turned from mundane to momentous to miraculous, the Mets weren't about to waste an opportunity.
"The plane had a mechanical problem they had to work on, so naturally we repaired to the airport lounge and had a few beverages," Swoboda said. "While we were in the bar, looking at the TV, Armstrong walked on the moon.
"It was another example of the good things that happened in 1969 for the New York Mets."
The team finally made it back to New York the next morning, carrying a 53-39 record, went 47-23 the rest of the regular season and stormed through the playoffs in one of the most unlikely World Series runs in baseball history.
Swoboda says now that Armstrong's moonwalk, the Mets' season and everything else going on in the world at that time created a powerful sense of place in time.
"It was transfixing," he says. "It was a very different time. We were in the thick of the Vietnam War, there was considerable anti-war protest, especially in New York. Woodstock would happen that summer [from Aug. 14-18], the love- and music-fest in upstate New York that we were still young enough to care about. You had good economic times because of the war industry.
"It was an amazing time when you consider all these things going on. And on top of all that, we were starting to roll as a team. This wonderful synergy started to take place. Everyone was healthy. Our pitching was great. And we more or less came out of the weeds and shocked everyone."
So as Swoboda sipped his drink and watched Armstrong prove American ingenuity with each monumental stride, one thing popped into his mind, and it remains there 40 years later.
"It just seemed like all things were possible," Swoboda says. "And when I think of all the things that were possible, [us winning the World Series] seemed like the longest shot of them all.
"But that's what happened."