Ohio (OH) is a state located in the Midwestern Region of the United States. Admitted to the Union as the 18th state on March 1, 1803, as the successor to the Northwest Territory, Ohio is the 6th most populous of U.S. states, with over 13 million inhabitants as of 1997. The capital and largest city of Columbus is also the 10th most-populous city in the nation (pop. 1,830,000); prior to 1816, the state capital was situated at Chillicothe (1803-1810 & 1812-1816) and Zanesville (1810-1812). Ohio also shares borders with Pennsylvania to the east, Virginia to the east/southeast, Kentucky to the south, Indiana to the west, and Michigan to the north, as well as maritime borders with Erie.