Skylab
1973-1979
The first US space station. Launched 14 May 1973 atop a Saturn V (without a spacecraft on top) and hosted three crews over 1973-74.
Specs
~77 t; 3 crews, ~170 crew-days in orbit; re-entered over the Indian Ocean / western Australia on 11 Jul 1979.
Why it matters
Proved humans can live and work in orbit for months - the direct precursor of the ISS. Its unguided 1979 reentry (debris scattered across Australia) is also a reminder that orbiting objects really do fall back down.