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. Skylab was constructed from a repurposed Saturn V third stage, and took the place of the stage during launch. Operations included an orbital workshop, a solar observatory, Earth observation and hundreds of experiments. From Wikipedia
