Skylab was the United States' first space station, and the second space station visited by a human crew. It was also the only space station NASA launched alone. The 100-ton space station was in Earth's orbit from 1973 to 1979 and it was visited by crews three times in 1973 and 1974. Skylab was launched 14 May 1973 by a Saturn INT-21 (a two-stage version of the Saturn V rocket) into a 235 nautical mile (435 km) orbit. The launch is sometimes referred to as Skylab 1, or SL-1.

Douglas Saturn V Rocket
Designed for the Apollo program at NASA's Marshall Space Flight Center, the Saturn V was first launched on November 9th, 1967. After two unmanned flight trials the Saturn V launched astronauts into lunar orbit in 1968, then in 1969 powered the first manned moon landing. The Saturn V's huge size and payload capacity dwarfed all other previously successful rockets. The Saturn V stood 363 feet tall and without fins was 33 feet in diameter with a payload capacity of 260,000 pounds. Its five powerful engines successfully pushed its 6.5 million pounds beyond the earth's atmosphere.