Numbers 501-506 were Lima Built for the US Army in 1942, but they were not the classic war time consolidations with export dimensions. This 500 class was redesignated the 400 class in June 1943 when the 550 Class engines showed up on the railroad during the war. The 550 class were all built by Baldwin except for the last unit number 562 was Alco built but looked identical. Locomotives nos. 501 and 502 were received and placed in service by the Alaska Railroad on May 30, 1942 and June 4, 1942 respectively.

Photo courtesy of The John Carrico Collection, Robert Graham Collection