On July 20, 1969, the Eagle module from Apollo 11 landed at Tranquility Base. Hours later, Neil Armstrong made history by becoming the first person to walk on the moon.
Originally inspired by the US' Cold War rivalry with the Soviet Union, the mission is now remembered as an iconic moment for stargazers all over the world.
Nasa marked the anniversary by streaming footage of the launch online, giving a new generation a chance to see the historic moment that was watched by half a billion people 50 years ago, the BBC reported.
At the moment the spacecraft landed, Apollo 11 commander Armstrong said: "Houston, Tranquility Base here. The Eagle has landed."
Charlie Duke, the capsule communicator, responded from mission control in Houston: "Roger, Tranquility. We copy you on the ground. You got a bunch of guys about to turn blue. We're breathing again."
Hours later, as he first stepped onto the moon's surface, he uttered the historic phrase: "That's one small step for man, one giant leap for mankind."
Armstrong was joined by his crewmates Buzz Aldrin and Michael Collins. All three were born in 1930, and although Aldrin and Collins are still alive, Armstrong died in 2012 at the age of 82.
Aldrin, the second person to walk on the moon, tweeted on Saturday: "Today, America put the big question to rest: We got there first. We landed on the moon with 250 million Americans watching our backs.
"The truth is: that mission belongs to all of them, and to future generations of Americans who dream to reach the moon once more."
Michael Collins, the third crew member, told Fox News that it's "not very often" he thinks about the mission.
Cities globally have held events to celebrate the landmark anniversary - including at Nasa's visitor centre Space Centre Houston, near the site of the Apollo 11 launch.
Military personnel put on a parachute display, and live bands performed. A New Year-style countdown will also mark the moment of Armstrong's first steps.
Artefacts from the mission have been exhibited at the Smithsonian's Air and Space Museum in Virginia, including the space suit Armstrong travelled in.
The Museum of Flight in Seattle also screened the original footage of the landing, recreating a 1969 living room complete with a contemporary TV.
( With inputs from IANS )