Port Huron & Detroit Railroad Company was incorporated on September 1, 1917, in the State of Michigan, United States of America, to own and operate 14 miles (23 km) of railroad track along the Saint Clair River from Port Huron, Michigan, to Marine City, Michigan. It remained in business until it was sold to the Chesapeake & Ohio Railroad (then part of Chessie System) in December 1984. Most of its original trackage is still being operated today by CSX Transportation Co. with whom Chesapeake & Ohio Railroad merged into on September 2, 1987.