Tulsa is the second-largest city in the state of Oklahoma and 47th-most populous city in the United States. As of July 2015, the population was 403,505, an increase of 11,599 over that reported in the 2010 Census. It is the principal municipality of the Tulsa Metropolitan Area, a region with 981,005 residents in the MSA and 1,151,172 in the CSA. The city serves as the county seat of Tulsa County, the most densely populated county in Oklahoma, with urban development extending into Osage, Rogers, and Wagoner counties.