Perry County is a county located in the U.S. state of Mississippi. As of the 2010 census, the population was 12,250. The county seat is New Augusta. The county is named after the War of 1812 naval hero, Oliver Hazard Perry.Perry County is part of the Hattiesburg, MS Metropolitan Statistical Area.Until 1906, the county seat was the old town of Augusta, near the center of the county on the east bank of the Leaf River.