When railroads were built in the early portion of the 19th century, travel became accessible to the masses. Until the railroads were built, the average American never traveled more than 20 miles from their homes in their lifetime. The railroads provided unimagined travel opportunities for people and freight. The first railroad came to Morris County in October 1837, when train service between Madison and Newark began on the Morris & Essex Railroad, which today is NJ Transit's Morristown Line. Service was extended to Morristown in January 1838, to Dover in August 1848, and to Hackettstown and Phillipsburg in November of 1865. The Morris & Essex Railroad was purchased by the Delaware, Lackawanna, & Western Railroad (DL&W) in the later half of the 1800's and became the Erie-Lackawanna Railroad in October 1866 when the DL&W and the Erie Railroad merged. The State of New Jersey purchased the commuter lines of the Erie-Lackawanna Railroad, which were operated by Conrail from April 1, 1976 until January 1, 1980 when New Jersey Transit assumed operation.

Two other interstate railroads served Morris County. The New York, Susquehanna & Western Railway, (formerly the New Jersey Midland Railway), which parallels Route 23 in the northern portion of the county, opened in April 1872. In July 1876, the Central Railroad of New Jersey opened a secondary line from its main line in High Bridge that served Chester, Long Valley, Flanders, Succasunna, Dover, Hibernia, Lake Hopatcong, and Sussex County. Morris County now owns much of the old Central Railroad of New Jersey tracks located within the county,some of which are used for freight service.