Ohio State Route 821

Ohio 821 is a relic of the old U.S. Highway 21 through southeastern Ohio between Cambridge, Ohio and Marietta, Ohio. It is entirely undivided surface road, and it is much less direct than the newer Interstate 77 which supplanted it as a through route. It is now entirely a local highway with a state highway marker.

As Interstate 77 was built, the designation U.S. 21 was moved to the freeway before Ohio wholly decommissioned the now-superfluous U.S. 21.