The ALCO PA-1/PB-1 was a 2,000 horsepower diesel locomotives built to haul passenger trains. Built between September 1946 and June 1950 . The locomotives were built in Schenectady, New York, in the United States by a partnership of the American Locomotive Company (ALCO) and General Electric (GE) between June 1946 and December 1953. Designed by General Electric's Ray Patten (along with their ALCO FA cousins), they were of a cab unit design; both cab-equipped lead A unit PA and cabless booster B unit PB models were built. While externally the PB models were slightly shorter than the PA model, they shared many of the same characteristics, both aesthetically and mechanically. However, they were not as reliable as EMD E-units.  ALCO's designation of P indicates that they were geared for higher speeds and passenger use, whereas the F designation marks these locomotives as being geared primarily for freight use. However, beyond this their design was largely similar - aside from the PA/PB's both being larger A1A-A1A types with an even more striking nose - and many railroads used PA and FA locomotives for both freight and passenger service.