American railroad company established in 1868 with the consolidation of two smaller lines, the Virginia Central and the Covington and Ohio. It subsequently acquired a number of other lines, culminating in its merger with the Pere Marquette Railroad Company in 1947.

The C&O acquired the Baltimore and Ohio Railroad in 1963 but continued to operate it as a separate system. In 1973 the Chessie System, Inc., was established as a holding company with the C&O as a subsidiary. The railroad operates mainly in Virginia, West Virginia, Kentucky, Ohio, Indiana, and Michigan. Half of its freight revenues are drawn from coal, with motor vehicles and parts also contributing significantly. Its passenger services were taken over by the National Railroad Passenger Corporation (Amtrak) in 1972.

In 1980 the Chessie System merged with Seaboard Coast Line Industries, Inc., operator of track extending from Washington, D.C., to Miami, New Orleans, St. Louis, and Chicago, to form the CSX Corporation (q.v.). The 17 railroad companies included in the new corporation are operated as separate entities, yet offer coordinated single-system transportation. Coal is the major cargo hauled. CSX also owns a large line of container ships and another of barge carriers.