Ohio. Ohio is a state in the Midwestern United States. Ohio is the 34th largest, 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 on March 1, 1803.he 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 on March 1, 1803.