Tulsa ( /ˈtʌlsə/) is the second-largest city in the state of Oklahoma and 46th-largest city in the United States. With a population of 391,906 as of the 2010 census, it is the principal municipality of the Tulsa Metropolitan Area, a region with 937,478 (2010) residents in the MSA and 988,454 (2010) in the CSA. Tulsa's CSA is projected to reach one million between 2010 and 2012. 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.