Franklin County is a county in the U.S. state of Ohio. As of the 2020 census, the population was 1,323,807, making it the most populous county in Ohio. Most of its land area is taken up by its county seat, Columbus, the state capital and most populous city in Ohio. The county was established on April 30, 1803, less than two months after Ohio became a state, and was named after Benjamin Franklin. Originally, Franklin County extended north to Lake Erie before it was subdivided into smaller counties. Franklin County is the central county of the Columbus, Ohio Metropolitan Statistical Area.