Fifty years ago this month, humans stepped onto the moon for the first time in history.

On July 16, 1969, the crew of NASA's Apollo 11 mission — astronauts Neil Armstrong, Buzz Aldrin, and Michael Collins — launched on a daring adventure. Four days later, on July 20, Armstrong and Aldrin landed a small spaceship on the lunar surface, crawled outside, and planted their boots into the ground along with an American flag and some scientific instruments.

Apollo 11 often hogs the history books, but many Apollo missions before it made the astronauts' conquest possible, and the missions that followed added to the program's long list of accomplishments. In total, NASA wound up putting 12 astronauts on the moon's surface. In the roughly five decades since then, however, no US spacecraft has returned with people.

That may soon change, though.

Read more: An astronaut explains why the Apollo 11 moon landing was not the NASA program's greatest moment

In March, Vice President Mike Pence vowed that the US would put astronauts back on the moon by 2024. The first year of the program may cost $1.6 billion, and the goal is to eventually build a permanent lunar base, mine ice from craters, and split that water into fuel for more ambitious space exploration, like crewed visits to Mars.

In November 2018, NASA also announced that it was offering up to $2.6 billion in contracts to nine American companies that could land robotic probes on the moon by 2022. NASA does not want to buy the lunar landers or take responsibility for launching, landing, or controlling them. Instead, the space agency wants the private sector to deal with those challenges and bid on the opportunity to take NASA's experiments to the moon.

NASA has since selected demonstration payloads that could go to the moon as part of that program — perhaps even by the end of this year.

Until new moon missions take off, here's a look back at all of NASA's Apollo missions, which flew between 1968 and 1972 and succeeded in putting the first humans on the moon.