The Pennsylvania Railroad's MP54 class of electric multiple unit cars was their first and largest class of this type of car. The class was initially constructed as an unpowered, locomotive hauled coach for suburban operations, but were designed with the capacity to be rebuilt into self-propelled MU 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. Eventually the cars came to be used throughout the railroad's electrified network from Washington, DC to New York City and Harrisburg, PA. The ubiquitous cars became a commuting tradition during their long years of serv