In the 1820s, the Baltimore & Susquehanna Railroad set out to construct a rail line extending from Baltimore to York Haven, a small town situated along the west shore of the Susquehanna River several miles downstream from Harrisburg.

In order to build in Pennsylvania, a separate corporation was formed, the York and Maryland Line Railroad Company. Upon reaching New Freedom, the railroad followed the south branch of the Codorus Creek to access York.

Just north of Gladfelters, the creek makes a long and tight oxbow curve around a granite wall, and the railroad engineers drilled through 300 feet of rock rather than twist the line around the wall. The tunnel was completed and opened to traffic in 1838, although the stone facework was not completed until 1840.

Due to the abundance of wartime traffic on the line during the Civil War, the rail line was double tracked, and the tunnel was rebuilt to accomodate the second track in the 1860s.

The Howard Tunnel is the oldest operating railroad tunnel in the United States, and the York County Heritage Rail Trail passes through the tunnel.

Some information on the history of Howard Tunnel was found in the book, "The Story of the Northern Central Railway," a Greenburg publication by Robert L. Gunnarson, ISBN 0-89778-157-0.