Skylab was the United States' first space station launched by NASA, occupied for about 24 weeks between May 1973 and February 1974. It was operated by three trios of astronaut crews: Skylab 2, Skylab 3, and Skylab 4. The manifestation of the Apollo Applications Program, Skylab was constructed from a repurposed Saturn V third stage (the S-IVB), a dry workshop, and took the place of the stage during launch. Operations included an orbital workshop, a solar observatory, Earth observation, ten spacewalks, and hundreds of experiments. NASA's station concept had competed with the Department of Defense's Manned Orbiting Laboratory concept from 1963 to 1969. Skylab was the world's second space station, after the Soviet space program's Salyut 1.

Wikipedia: https://en.wikipedia.org/wiki/Skylab. Related NASA reference: https://nssdc.gsfc.nasa.gov/planetary/chronology.html#1973. Description adapted from Wikipedia contributors (CC BY-SA 4.0; https://creativecommons.org/licenses/by-sa/4.0/).