When Amtrak took over (most of) America's passenger rail operations in May 1971, they had to make due with a hodge-podge of diesels, mainly E-units, built in the 1940s and 1950s that were, to put it kindly, getting a bit tired. New power was ordered from EMD - a new model, the SDP40F - which began arriving just about two years after Amtrak's inaugural day. The first of these 500-class engines entered service on the former Santa Fe trains - notably, trains #3 and #4, the Chicago to Los Angeles Southwest Limited. With a built date of July 1973, Amtrak 508 is seen at Los Angeles Union Passenger Terminal on July 9th, 1973 after having brought in that morning's #3. These engines were basically passenger versions of EMD's popular SD40-2, in a cowl carbody (reminiscent of EMD's FP45) and including two steam generators and, because they were to operate nationwide, two types (Buckeye and Snyder) of fuel fillers. (On an adjacent track can be seen a bit of a Santa Fe F7A, which were still powering Amtrak's L.A. to San Diego San Diegans, and which were still owned by Santa Fe and leased to Amtrak. Within a very short time, SDP40Fs would replace these classic Fs as well.)
