In the late 1980s NASA began to consider replacing its previous neutral-buoyancy training facility, the Weightless Environment Training Facility (WETF). The WETF, located at Johnson Space Center, had been successfully used to train astronauts for numerous missions, but its pool was too small to hold useful mock-ups of space station components of the sorts intended for the mooted Space Station Freedom, or its successor, the International Space Station.
This new pool was going to be on Johnson Space Center property and was planned to be 72 meters (235 ft) by 41 meters (135 ft), with a depth of 18 meters (60 ft). To save money it was downsized and placed inside an existing structure.
NASA purchased the structure that now holds the NBL from McDonnell Douglas in the early 1990s and began refitting it as a neutral-buoyancy training center in 1995.