Skylab was the first space station launched in 1973. It was a United States project and the first American space station to orbit Earth. Skylab was the only space station launched by the United States until the launch of the International Space Station in 1998. Skylab was in operation for six years and hosted three crews of astronauts. The station was used to conduct scientific experiments and observations of Earth and the solar system. Skylab was eventually de-orbited and re-entered Earth's atmosphere in 1979.