State Route 4, formerly known as Inter-county Highway 4 until 1921 and State Highway 4 in 1922, is a major north–south state highway in Ohio. It is the fifth longest state route in Ohio. Its southern terminus is at U.S. Route 42 in Cincinnati, Ohio, and its northern terminus is at U.S. Route 6 in Sandusky, Ohio. Its path is nearly ruler-straight for many miles. Some portions of the route are still marked as Dixie Highway. The northern portion was constructed by the Columbus and Sandusky Turnpike Company, see Turnpike Lands.

U.S. Route 6 (US 6) is a part of the United States Numbered Highway System that runs from Bishop, California, to Provincetown, Massachusetts. In Ohio, the road runs west–east from the Indiana state line near Edgerton to the Pennsylvania state line near Andover. The 248.002 miles (399.121 km) that lie in Ohio are maintained by the Ohio Department of Transportation (ODOT). US 6 serves the major cities of Sandusky, Lorain, and Cleveland. The highway is also called the Grand Army of the Republic Highway to honor the Union forces of the U.S. Civil War. The alternate name was designated in 1953.