In 1867, the Maryland Central Railroad was chartered with building a railroad line connecting Baltimore, MD, with Philadelphia, PA; however, no tracks were laid. It was not until 1873 that the first narrow-gauge tracks were laid by the Peach Bottom Railway connecting York, PA with Peach Bottom, PA on the Susquehanna River. Three other railroad charters were established to connect this trackage to Baltimore, which was still without railroad service, but none came to pass.

The Baltimore and Delta Railway began building narrow-gauge trackage in 1878 at Baltimore; while modest at first, the line continued stretching northwards until it connected to the Peach Bottom Railway at Delta, PA. The Maryland Central, which still existed, purchased both lines in 1889; in 1891, both lines came under the ownership of a newly-formed company, the Baltimore and Lehigh Railroad, which began to operate the entire line between York and Baltimore as a singular route.

The B&L was ill-fated, however, and filed for bankruptcy as early as 1893. As a result, the line from Delta north to York, and the line south of Delta to Baltimore, were purchased and again operated by two separate entities: the York Southern Railroad purchased the northern part, while a former owner of the B&L purchased the southern part and continued to operate it as the B&L. The entirety of the route was operated in this manner for another 6 years; even the northern part of the line was converted to standard gauge, while the southern portion remained narrow gauge.

In 1899, both lines came under the same ownership again, this time as the Maryland and Pennsylvania Railroad. The M&P, or "Ma & Pa Railroad", saw long-time success, offering both passenger and freight traffic between York and Baltimore. As to be expected, passenger service declined in the 1940s due to ever-increasing automobile traffic; indeed, passenger service ceased on August 31, 1954. Soon after, the southern part of the line, between Baltimore and Delta, was abandoned in 1958.

The northern section continued to operate, however, for another 20 years. The last train ran in 1984, and the tracks were pulled up in 1986. A short segment was left in place for the Maryland and Pennsylvania Railroad Preservation Society, with hope to once again run trains (albeit for passenger excursions) over the former Ma & Pa Railroad.