Ohio is a state in the midwestern united states. ohio is the 34th most extensive, the 7th most populous, and the 10th most densely populated of the 50 united states. the state's capital and largest city is columbus. the name "ohio" originated from iroquois word ohi-yo’, meaning "great river" or "large creek". the state, originally partitioned from the northwest territory, was admitted to the union as the 17th state (and the first under the northwest ordinance) on march 1, 1803.