This GP7L was built for the US Army as number 1821 (builder number 15691) in 1951. The Alaska Railroad purchased it in 1960 and rebuilt it in 1976 as GP7u number 1810. The Alaska Railroad sold it in 198? to Nevada Industrial Switching (NIS). In 1999 it was sold to Oregon Pacific Railway who in turn sold it to Samuel Industries. (Anchorage yard, November 3, 1971)
Number 1821 was used as a trail for rebuild by Morrison-Knudsen at Boise, Idaho. The rebuild added 100 horsepower, installed a modular electrical system, overhauled the prime mover and added a new AAR-type control stand. It returned to Alaska in October 1975 and was placed into mixed service between Anchorage and Whitter. In June 1976 the locomotive's number was changed to 1810.
The remaining nine GP7s went to the Illinois Central Gulf at Kentucky for rebuild. Special crew cab arctic heaters and winterized kits were also added. The winterization hatch allowed hot air exhaust to be vented out in the summertime and back down in the winter time to warm the alternator, compressor and other components.