Marion, OH is located about 45 minutes north of Columbus, OH on US Highway 23.
According to the U.S. Census Board, the county has a total area of 404 square miles. It is the fifth-smallest county in Ohio by total area. As of the 2000 census, there were 66,217 people, 24,578 households, and 17,253 families residing in the county. The population density was 164 people per square mile. There were 26,298 housing units at an average density of 65 per square mile.