ALCO RS-1
The ALCO RS-1 was a 4-axle diesel-electric locomotive built by Alco-GE between 1941 and 1953 and the American Locomotive Company from 1953 to 1960. ALCO subsidiary Montreal Locomotive Works built an additional three RS-1s in 1954. This model has the distinction of having the longest production run of any diesel locomotive for the North American market. The RS-1 was in production for 19 years from the first unit Rock Island #748 in March 1941 to the last unit National of Mexico #5663 in March 1960. Design. In 1940, the Rock Island Railroad approached ALCO about  building a locomotive for both road and switching service. To meet the Rock Island's request, ALCO created the RS-1. Their new design was a hood unit, in contrast to most existing locomotive designs at the time which were predominantly carbody units. The hood unit design allowed for improved visibility, especially to the rear. Rear visibility is very important for switching, which often involves reverse movements. Unlike carbody units, hood units such as the RS-1 can be operated in reverse without much difficulty, eliminating the need to turn them around at the end of a line. For these reasons, most  North American locomotives built since have followed this basic design, which is known as the road switcher. Though the locomotive could operate in either direction, the "long" hood was officially designated as the front. Production. The first thirteen production locomotives were requisitioned by the US Army, as U.S. involvement in World War II began shortly after ALCO began production. The five railroads affected had to wait while replacements were manufactured. The requisitioned RS-1s were remanufactured by ALCO into six axle RSD-1s for use on the Trans-Iranian Railway to supply the Soviet Union during the war. Variants. RSD-1: An RS-1  with two three axle trucks instead of the normal two axle trucks. The three axle trucks allowed the locomotive to operate safely on lighter track, as its weight was more evenly distributed by the additional axles. Unlike the RSC-1, all axles were powered. RSC-1: An RS-1 with three-axle trucks, having an A1A-A1A wheel arrangement. It was used in much the same manner as the original variant, though the axle load was distributed for operation on light rail such as are found on branch lines. Operating History. RS-1s were primarily operated in freight service, though in some cases they  were also assigned to passenger trains. A few railroads equipped their RS-1s with steam heading equipment for passenger trains. Many RS-1s were stationed in train yards for switching duties, assembling and taking apart trains to be hauled by mainline locomotives. True to their designation as 'road switchers', RS-1s could also be frequently found hauling mainline trains, especially on branch lines. The RS-1 enjoyed a long service life, despite its manufacturer ALCO shutting down in 1969, just 9 years after the last locomotive was produced. Despite ALCO's closure, spare parts have been produced and marketed by other manufacturers for the  RS-1 and other ALCO products. Many served for decades, and even in the 21st century a number of examples can still be found in freight service on shortline railroads, or on excursion trains at railroad museums. Successors. The RS-1 was succeeded by two improved versions in ALCO's catalogue, the RS-2 and RS-3. Despite this, the RS-1 remained in production even after both of its successors were discontinued. Preservation. Several examples exist at tourist railways and railway museums, including: External links. Diesel Shop roster with all data from Extra 2200 South http://www.thedieselshop.us/Alco_RS1.HTML