The Markland Locks and Dam is a concrete dam bridge and locks that span the Ohio River. It is 1395 feet (425.2 m) long, and connects Gallatin County, Kentucky, and Switzerland County, Indiana. The locks and dam were reviewed by the Board of Engineers for River and Harbours to replace the Ohio River locks and dams Number 35, 36, 37, 38 and 39. Then the project was approved by the Secretary of the Army on March 11, 1953. Construction on the locks began in March 1956 and they were placed in operation in May 1959. The dam construction began in April 1959 and was finished in June 1964.