The Pennsylvania Railroad acquired these locomotives in 1947. In the name, the "P" stands for "passenger", the "A" stands for the cab unit, the "B" stands for "booster" unit, and the "1" refers to Alco first model of this type. Alco also made model 2 and 3 (PA/B-2, PA/B-3). The PA was 65ft long, 14ft tall, and 11ft wide. The trucks were of the A-1-A configuration, where the center wheels were not powered but rather were used to distribute the weight. The PA-1 came in at 306,000 lbs. The PRR class was AP20 (Alco, passenger, 2000 hp). The PRR owned 10 PA's and 5 PB's. The photo on the right of #5755 came from the Fallen Flags web site. An additional reference is the book "Pennsylvania Railroad" (1997, MBI Publishing Company, ISBN 0-7603-0379-7, pg 115).

Kato released these locomotives in 1998. I converted the engines to DCC using the Digitrax' DN145K decoder.