Oklahoma City is the capital of the U.S. state of Oklahoma and its largest city. The county seat of Oklahoma County, the city ranks 29th among United States cities in population. As of the 2012 census, the population was 599,199. In 2010 the Oklahoma City metropolitan area had a population of 1,252,987, and the Oklahoma City-Shawnee Combined Statistical Area had a population of 1,322,249 residents, making it Oklahoma's largest metropolitan area. Oklahoma City's city limits extend into Canadian, Cleveland, and Pottawatomie counties, though much of those areas outside of the core Oklahoma County area are suburban or rural. The city ranks as the eighth-largest city in the United States by land area.Oklahoma City features one of the largest livestock markets in the world. Oil, natural gas, petroleum products and related industries are the largest sector of the local economy. The city is situated in the middle of an active oil field and oil derricks dot the capitol grounds. The federal government employs large numbers of workers at Tinker Air Force Base and the United States Department of Transportation's Mike Monroney Aeronautical Center.Oklahoma City lies along one of the primary travel corridors into Texas and Mexico. Located in the Frontier Country region of the state, the city's northeast section lies in an ecological region known as the Cross Timbers. The city was founded during the Land Run of 1889, and grew to a population of over 10,000 within hours of its founding. The city was the scene of the April 19, 1995 bombing attack of the Alfred P. Murrah Federal Building, in which 168 people died. It was the worst terror attack in the history of the United States until the attacks of September 11, 2001, and remains the worst act of domestic terrorism in U.S. history.Since the time weather records have been kept, Oklahoma City has been struck by nine strong tornadoes, eight F/EF4s and one F5. On May 3, 1999, parts of southern Oklahoma City and nearby communities suffered one of the most powerful tornadoes on record, registering as an F5. On May 20, 2013, southern Oklahoma City, Moore, and other surrounding areas and suburbs were struck by another devastating EF5 tornado.