The San Francisco Bay Area had long been a major site of U.S. Navy work, as well as the site of the Navy's large research airfield at Moffett Field. A number of technology firms had set up shop in the area around Moffett to serve the Navy. When the Navy moved most of its West Coast operations to San Diego, NASA took over portions of Moffett for aeronautics research. Many of the original companies stayed, while new ones moved in. The immediate area was soon filled with aerospace firms.