High Quality Content by WIKIPEDIA articles! Fulton County is a county located in the U.S. state of Georgia. Its county seat is Atlanta, the state capital since 1868 and the principal county of the Atlanta metropolitan area. At the 2010 United States Census, the population was 920,581; however, Atlanta mayor Kasim Reed suspects significant undercounting in the City of Atlanta, which implies similar concerns for Fulton County as a whole – the 2009 estimate of the county`s population was 1,020,014, 10.8% higher than the 2010 census results.