The class was initially constructed as an unpowered, locomotive hauled coach for suburban operations, but were designed to be rebuilt into self-propelled units as electrification plans were realized.

The first of these self-propelled cars were placed in service with the PRR subsidiary Long Island Rail Road with DC propulsion in 1908 and soon spread to the Philadelphia-based network of low frequency AC electrified suburban lines in 1915.

[7] The cars ran in service with the PRR until the Penn Central merger in 1968 at which point they were already being marked for replacement by new technology railcars such as the Budd M1 and Pioneer III.

After the bankruptcy of the Penn Central the remaining MP54s found themselves being operated by Conrail under contract with local commuter rail authorities.

In 1906, during the PRR construction project to build tunnels under the Hudson and East Rivers and build Penn Station, the PRR announced that all new passenger cars would be made of steel and that wooden cars would not be allowed in the tunnels due to the hazard of fire.

Simultaneously, the same electrical system was being installed for use in the Hudson River tunnels and west to Manhattan Transfer, just east of Newark for use by the PRR proper.

[14] Penn Station opened September 8, 1910, with service to Long Island points being provided by LIRR MP54 cars.

[16] In addition to the cars built for the PRR and LIRR, the West Jersey and Seashore Railroad (which later became part of the Pennsylvania-Reading Seashore Lines) received a small fleet of eighteen 650 V DC powered MP54 cars for use on its electrified interurban line between Camden, Millville, and Atlantic City in 1912.

Each car received a pantograph, a transformer, a power truck, a motorman's cab and controls at each end, and MU circuits.

The MP54s were rebuilt at PRR's Wilmington, DE electric shops with an initial batch of fifty 450-horsepower (340 kW) cars in the class MP54E5.

[28] A follow-up batch of fifty 508 hp cars in the class MP54E6 were rebuilt at the Altoona shops (for unknown reasons, the designation MP54E4 was skipped).

While state of the art in 1908, when the last brand new MP54 rolled off the assembly line 28 years later, the design did more to suit the PRR's desire for standardization than the comfort of the passengers that rode them.

[31] The 1908 truck design provided little in the way of ride quality, and friction bearings on unmodified cars retarded performance further.

For many years a single car was used on a run between South Amboy and Trenton via Jamesburg, mainly to transport high school students.

For popular events, particularly the Army-Navy football games in Philadelphia, MP54 cars were used to make up some of the special trains to provide the needed transportation.

These included AT&SF (Santa Fe), BC&G (Buffalo Creek and Gauley),[38] B&M (Boston and Maine), Erie, Lackawanna, Ligonier Valley Railroad,[48] [verification needed] NYS&W (New York Susquehanna and Western, Susquehanna), N&W (Norfolk and Western), Piedmont and Northern and Tuckerton.

Additional road names reported as possible: CR (Conrail), Union Transportation (Pemberton & Hightstown), Consolidades de Cuba, and the Midland Continental.

[49] In 1907, prior to the purchase of its MP54D's, the West Jersey and Seashore Railroad expanded its wooden interurban fleet operating its electrified service from Camden to Atlantic City and Millville with an order of porthole-window cars, designated MP2.