This, the final flight of the Apollo spacecraft, was the first docking of spacecraft built by different nations and presaged the era of cooperation between the Russians and the Americans that is now such an essential part of our efforts to build a permanently occupied space station.
The American crew included three-flight veteran Thomas P. Stafford, rookie Vance Brand, and the last of the original seven Mercury astronauts to make it into orbit, Donald K. "Deke" Slayton, whose heart murmur had previously kept him grounded. The Soviet crew included the first space walker, Alexei Leonov, and rookie Valeri Kubasov.
While this mission is generally remembered as a political/public relations venture, it resulted in some major technological advancements necessitated by the requirement to dock the two extremely variant spacecraft, neither of which had been built for the purpose, together.
The two spacecraft were launched within seven and a half hours of one another, and, three hours after they docked two days later, the Astronauts and Cosmonauts met in the middle ahd shook hands in orbit, exchanged flags and gifts (including the seeds of trees that were later planted in each others' countries) and conversed haltingly with one another in each other's native tongues.
It would be six long years before another American astronaut would fly in space, this time aboard the reusable Space Shuttle. The Apollo era, an era of the greatest achievements in mankind's history, had ended.