Edwards Air Force Base was the cradle and nursery for aerospace in the jet age, and continues to be the nation’s primary aviation research and evaluation field test base. As many as 10,000 people work within its 480 square miles of land in the desert north of Palmdale, at Rogers Dry Lake. Tenants include the Armstrong Flight Research Center (formerly Dryden Flight Research Center), NASA’s primary atmospheric flight research and test facility, and the Air Force’s Air Force Test Center, test pilot school, and propulsion research test site on Leuhman Ridge. Hangars and structures for current and past aviation projects line the western shore of the dry lake from South Base, where the loading pit for the Bell X-1 (the first plane to break the sound barrier) is preserved, and the latest stealth bombers are tested, to North Base, with the remains of a Jet Propulsion Lab rocket fuel research facility. In between, facilities at the main base include the largest anechoic chamber in the nation, and the Air Force Flight Test Museum (which is not accessible to the general public). On a ridge near the main base are high powered cameras that track objects in space, as well as test aircraft flying in the restricted airspace known as R-2508, which covers most of the northern Mojave.