Dayton (/ˈdeɪtən/) is the sixth-largest city in the state of Ohio and is the county seat of Montgomery County. A small portion of the city extends into Greene County. In the 2010 census, the population was 141,527, and the Dayton metropolitan area had 799,232 residents, making it Ohio's fourth-largest metropolitan area, after Cleveland, Cincinnati, and Columbus and the 63rd-largest in the United States. The Dayton-Springfield-Greenville Combined Statistical Area had a population of 1,080,044 in 2010, making it the 43rd-largest in the United States. Dayton is within Ohio's Miami Valley region, just north of the Cincinnati–Northern Kentucky metropolitan area.