Apollo and Soyuz 19 launched 1975

Apollo-Soyuz Test Project commemorative painting

On what would be the last mission of NASA's Apollo program, "Apollo 18" (the unofficial designation) was launched July 15, 1975 for the first joint space mission between the United States and the Soviet Union. Its crew consisted of Thomas Stafford, Vance Brand and Donald "Deke" Slayton.

On the other side of the world, Soyuz 19 launched with cosmonauts Alexey Leonov and Valeri Kubasov the same day. The mission was called the Apollo-Soyuz Test Project.

When the ships docked, the crews exchanged the first international handshake in space.  They also conducted experiments, exchanged flags and gifts, ate together and signed certificates. After 44 hours together, the ships separated and went their separate ways. 

The cosmonauts stayed in space for two more days, returning to Earth July 21. The astronauts stayed five extra days and returned to Earth July 24.