[3] The county is named for Thomas Jefferson, who was vice president at the time of its creation.

[5] 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.

In the meantime, settlers had built homes around the fort; they named their settlement La Belle.

During the first half of the 19th 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.

As of the 2010 United States census, there were 69,709 people, 29,109 households, and 18,713 families living in the county.

[12] In terms of ancestry, 20.0% were German, 17.1% were Irish, 12.9% were Italian, 9.1% were English, 8.3% were Polish, and 4.6% were American.

In 2012, Mitt Romney became the first Republican candidate to win the county since it voted for President Nixon in the 1972 presidential election.

[17] Commercial air service is available at nearby Pittsburgh International Airport to the east via U.S. Route 22.