Ohio -en-us-Ohio. oggoʊˈhaɪ. oʊ- is a Midwestern state in the United States. The 34th largest state by area in the U.S. it is the 7th-most populous with nearly 11.5 million residents containing several major American cities and seven metropolitan areas with populations of 500 000 or more. The state's capital is Columbus. The Anglicized name Ohio comes from the Iroquois word ohi-yo’ meaning 'great river'.