Ohio was not part of the original 13 states. In fact, the area around northeast Ohio was, at one time, part of Connecticut's "Western Reserve." Just when DID the Buckeye state enter the union?
Ohio became the 17th United State on March 1, 1803, just seven years after Moses Cleaveland landed near Conneaut Creek and began to survey the area. At the time it became a state, Ohio had a population of around 45,000 people.
technically Ohio did not become a state until 1953. It seems that when the Buckeye State was planning its 150th-anniversary celebration, someone tried to look up the paperwork and found that a state charter was never filed. There's some confusion as to why or if Ohio really needed one at the time. (Ohio was the first state created out of a territory, which led to most of the confusion; Vermont, Tennessee, and Kentucky already had governments in place before they applied for statehood.) Just to be thorough, however, an Ohio congressman in 1953, George Bender, introduced a bill in Congress to declare Ohio a state. It was quickly passed and signed into law by President Eisenhower. You can read all of the details about the situation on The Green Papers.com.