Ohio, one of the Midwestern states of the United States. It is bounded by Michigan, Pennsylvania, West Virginia, Kentucky, and Indiana. Lake Erie forms part of the northern border. The Ohio River forms the entire southern border. With a total area of 44,828 square miles (116,103 km2), Ohio is the 34th state in size. Ohio is one of the most heavily populated state and a leader in industrial and agricultural production.Ohio's state bird is the cardinal.