Oklahoma City is the capital of the U.S. state of Oklahoma. The county seat of Oklahoma County, the city is the 30th largest in the Unite States The city's estimated population as of 2006 was 537,734, with a 2006 estimated population of 1,192,989 in the metropolitan area. In 2007, the Oklahoma City-Shawnee Combined Statistical Area had a population of 1,262,027 residents. Besides Oklahoma County, the city extends into Canadian, Cleveland, and Pottawatomie counties. Founded during the Land Run of 1889, Oklahoma City was the site of the bombing of the Alfred P. Murrah Federal Building in 1995, the largest act of terrorism on American soil prior to the September 11, 2001 attacks and the most destructive act of domestic terrorism in American history.