National Security Agency (NSA) Headquarters, Maryland

Located on the grounds of Fort Meade, the headquarters for the nation's premier covert intelligence gathering organization are housed in two high-rise office structures, built and dedicated by Ronald Reagan in 1986, and in other structures on the base, including an estimated 10 acres of which are underground. At least 20,000 employees work for the NSA at Fort Meade, making it the largest employer in the county, one of the largest employers in Maryland, and the largest employer of mathematicians in the country. While the extent of NSA's technical facilities is guarded as a national security measure, the NSA's headquarters is believed to house one of the most powerful supercomputers in the world. The NSA operates other computer labs, offices, and satellite interception posts around the world.