Jefferson County is a county located in the U.S. state of Ohio. As of the 2020 census, the population was 65,249. Its county seat is Steubenville. The county is named for Thomas Jefferson, who was vice president at the time of its creation.
Jefferson County is part of the Weirton-Steubenville, WV-OH Metropolitan Statistical Area, which is also included in the Pittsburgh-New Castle-Weirton, PA-WV-OH Combined Statistical Area.
Jefferson County was organized on July 29, 1797, by proclamation of Governor Arthur St. Clair, six years before Ohio was granted statehood. Its boundaries were originally quite large, including all of northeastern Ohio east of the Cuyahoga River, but it was divided and redrawn several times before assuming its present-day boundaries in 1833, after the formation of neighboring Carroll County.
In 1786, the United States built Fort Steuben to protect the government surveyors mapping the land west of the Ohio River. When the surveyors completed their task a few years later, the fort was abandoned. In the meantime, settlers had built homes around the fort; they named their settlement La Belle. When the county was created in 1797, La Belle was selected as the County seat. The town was subsequently renamed Steubenville, in honor of the abandoned fort.
During the first half of the nineteenth century, Steubenville was primarily a port town, and the rest of the county consisted of small villages and farms. However, in 1856, Frazier, Kilgore and Company erected a rolling mill (the forerunner of steel mills) and the Steubenville Coal and Mining Company sank a coal shaft, resulting in Jefferson County becoming one of the leading centers of the new Industrial Revolution.