Franklin County is a county located in the state of Ohio, United States. According to the 2010 census, it has a population of 1,163,414, which is an increase of 8.8% from 1,068,978 in 2000.It is the second largest county in Ohio (after Cuyahoga County) and the 34th largest county in population in the United States. Franklin County is also the largest in the eight-county Columbus, Ohio Metropolitan Statistical Area. Its county seat is Columbus,[3] which is located in the middle of the county. Columbus is the capital and largest city in Ohio, as well as the 15th largest city in the United States, according to the U.S. Census Bureau's 2005 Population Estimates. Columbus makes up about 66.56% of the population of the county, the rest being provided by various suburbs and townships, and Franklin County itself makes up about 9.42% of the state population as of 2000.