On July 17, 1975, Thomas Stafford of the United States shook hands with Alexei Leonov of the Soviet Union.

That may not sound like a big deal, but the greeting took place in orbit above the Earth inside the docking ring of joined Apollo and Soyuz spacecraft.

The final flight of the Apollo program was the first flight in which spacecraft from different nations docked in space.

The U.S. Apollo spacecraft carrying a crew of three met the Russian Soyuz spacecraft with its crew of two – the culmination of five years’ of work and planning for the first joint space mission.

Up until 1969, the U.S. and Soviet Union had been engaged in a space race. The Soviet Union took an early lead, putting up the first man in space and the first spacewalker, but the ultimate prize, the Moon landing, went to the United States.

In addition to Stafford, the Apollo crew included Donald K. “Deke” Slayton, docking module pilot, and Vance D. Brand, command module pilot.

The Soyuz 19 crew also included Valeri N. Kubasov, flight engineer.