Franklin County is a county in central Ohio. It is 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. Franklin County originally extended north to Lake Erie before being subdivided into smaller counties.

Franklin County, particularly Columbus, has been a centerpiece for presidential and congressional politics, most notably the 2000 presidential election, the 2004 presidential election, and the 2006 midterm elections. Franklin County is home to one of the largest universities in the United States, Ohio State University, which has about 60,000 students on its main Columbus campus.

On March 30, 1803, the Ohio government authorized the creation of Franklin County. The county originally was part of Ross County. Residents named the county in honor of Benjamin Franklin. In 1816, Franklin County's Columbus became Ohio's state capital. Surveyors laid out the city in 1812, and officials incorporated it in 1816. Columbus was not Ohio's original capital, but the state legislature chose to move the state government there after its location for a short time at Chillicothe and at Zanesville. Columbus was chosen as the site for the new capital because of its central location within the state and access by way of major transportation routes (primarily rivers) at that time. The legislature chose it as Ohio's capital over a number of other competitors, including Franklinton, Dublin, Worthington, and Delaware.

On May 5, 1802, a group of prospective settlers founded the Scioto Company at the home of Rev. Eber B. Clark in Granby, Connecticut, for the purpose of forming a settlement between the Muskingum River and Great Miami River in the Ohio Country. James Kilbourne was elected president and Josiah Topping secretary. On August 30, 1802, James Kilbourne and Nathaniel Little arrived at Colonel Thomas Worthington's home in Chillicothe. They tentatively reserved land along the Scioto River on the Pickaway Plains for their new settlement.