Santa Fe was the first railroad to get FT freight diesels and began accumulating them (IIRC) in January, 1941. By the end of of FT production in 1945, Santa Fe had acquired 320 of EMD's production of 1096 units or almost 30% of EMD's total production.

Santa Fe ran through some very arid and heavily graded territory. If you check the grade profile between Los Angeles and Needles, Santa Fe's line is either climbing or descending a grade most of the way. From Needles to about Flagstaff, Santa Fe has a 141 miles of continuous grade with a ruling grade of 1.42% and an average grade of 1%. What with the requirement for water and the fact that steam is at a disadvantage at slow speeds compared to diesels, it's no surprise that Santa Fe's freights were almost completely dieselized between Los Angeles and Winslow, AZ (IIRC) by the end of WWI, with steam being assigned as helpers where necessary.

Santa Fe's wide ranging experience with diesels during WWII was followed by a major effort to replace steam with diesel. By comparison, rival Southern Pacific didn't order a road freight diesel until 1947, six years after Santa Fe got its first FT units. Santa Fe was also an early adopter of the EMD GP7, amassing  more than 200 units between October, 1950 and Dec., 1953. Again by comparison, Southern Pacific bought no GP7's and only began acquiring EMD hood units in 1954 when the GP9 was introduced.

Steam on the Santa Fe actually lasted until 1957, but after 1953, was only seasonal. The last use of steam was in Abo Canyon in New Mexico, where some 4-8-4's and 2-10-4's were used as helpers during the summer of 1957. 4-8-4 #3780 was used on the last steam helper trip on August 27,1957.  http://www.wheelsmuseum.org/stagner.html

Mike

Mike, you are a wealth of information. You described the Santa Fe transition process in good detail. Perhaps you have similar knowledge for the UP ?

P.S. You may want to edit your comment here:

"... it's no surprise that Santa Fe's freights were almost completely dieselized between Los Angeles and Winslow, AZ (IIRC) by the end of WWI, with steam being assigned as helpers where necessary."

I believe you meant to say "by the end of WWII"

In fact the water situation was so bad that it was one of the few, perhaps only railroad permitted to buy diesel locomotives during WW2.  What water was available in the Southern California desert, Arizona, and I think New Mexico was so full of alkali that it was useless for a steam engine.  The Santa Fe used to run "unit trains" of tank cars full of water to service water tanks all over the desert.

I believe you meant to say "by the end of WWII"

Yup. Probably easier to refer to it as WW2 than WWII.

Mike

In fact the water situation was so bad that it was one of the few, perhaps only railroad permitted to buy diesel locomotives during WW2

Since FT production essentially encompassed US involvement in WWII, there were actually quite a few railroads getting FT's during the war

Among those (and this is not an exhaustive list by any means):

AT&SF, GN (2nd largest recipient after Santa Fe), NP, WP, Cotton Belt, B&O, D&RGW, MP, Seaboard, Southern, ACL, B&M, Milwaukee, M&StL, and CB&Q.

In addition, the New Haven managed to snag a number of Alco DL-109's as they were used as dual service power.

Mike