The Middletown and Unionville Railroad, successor to the Middletown, Unionville and Water Gap Railroad, operated from December 1, 1913, until May 31, 1946, when it was reorganized as the Middletown and New Jersey Railway. The railroad's main revenue was derived from the transportation of dairy products, feed, coal, lumber, and passengers along its 14.5-mile right-of-way from the city of Middletown through Slate Hill, Johnson, Westtown, and Unionville in Orange County, New York. It provided a connection between the Erie Railroad in Middletown; the New York, Ontario & Western Railway in Middletown; and the New York, Susquehanna & Western Railroad in New Jersey. All three of these railroads had unique relationships with the M&U during its period of operation.