To continue the same subject:
(Note: I wasn't asking about the Putnam but I'll throw this item in anyway)
I understand from photos that the dieselization of the Put began on or about July 15 1951 with the delivery of the first of the Lima hoods (according to a Trains Magazine photo). The final steam run occurred on September 29 (according to the dates on photos in Put books). There was no "Celebrated" event, just a regular train departure out of Yorktown Hts. For that 2 1/2 months, between july 15 and Sept. 29, the new Limas and the elderly 4-6-0s "coexisted" on Put trains
(It may sound strange that the Put dieselized a whole year before the Harlem but there was a good reason for it: the construction of the Deegan Expressway in The Bronx was taking away the Put's steam coaling and watering facilities at Sedgwick Avenue.)
Over on the Harlem: in the summer of 1952 steam was still the thing, except that I think the the "Rut Milk" freights were diesel.
The 8200 series Alco RS-3s were delivered in July 1951 (according to their builder's plates.) What service they were placed in I do not know. All I know for sure about the end of Harlem steam was that the last run occurred on Sept. 11 1952, and was photographed in a couple of locations (Pleasantville and North White) by well known NYC photographer . It was a regular run, not a celebrated trip of any kind