Tulsa is the second-largest city in the state of Oklahoma and 46th-largest city in the United States. With an estimated population of 385,635 in 2008, it is the principal municipality of the Tulsa Metropolitan Statistical Area, a region of 916,079 residents projected to reach one million between 2010 and 2012. In 2008, the Tulsa-Bartlesville Combined Statistical Area had a population of 966,531 residents. The city serves as the county seat of Tulsa County, the most densely populated county in Oklahoma, and extends into Osage, Rogers, and Wagoner counties. Tulsa was first settled in the 1830s by the Lachapoka Band of Creek Native American tribe. In 1921, it was the site of the infamous Tulsa Race Riot, one of the largest and most destructive acts of racial violence in the history of the United States. For most of the 20th century, the city held the nickname "Oil Capital of the World" and played a major role as one of the most important hubs for the American oil industry. Tulsa, along with several other cities, claims to be the birthplace of U.S. Route 66. Tulsa is also known for its Western Swing music. Once heavily dependent on the oil industry, economic downturn and subsequent diversification efforts created an economic base in the energy, finance, aviation, telecommunications and technology sectors. The Tulsa Port of Catoosa, at the head of the McClellan-Kerr Arkansas River Navigation System, is the most inland river port in the U.S. with access to international waterways. Two institutions of higher education within the city operate at the NCAA Division I level, Oral Roberts University and the University of Tulsa. Located in Tornado Alley, the city frequently experiences severe weather. It is situated on the Arkansas River at the foothills of the Ozark Mountains in northeast Oklahoma, a region of the state known as "Green Country. " Considered the cultural and arts center of Oklahoma, Tulsa houses two world-renowned art museums, full-time professional opera and ballet companies, and one of the nation's largest concentrations of art deco architecture. The city has been called one of America's most livable large cities by Partners for Livable Communities, Forbes, and Relocate America. People from Tulsa are called "Tulsans."