I'm guessing, here, but…
I'd say about 70th or 71st street. Enter Riverside Park at its extreme south end (72nd Street and Riverside Drive), go as far down toward the river as you can, turn left.
There was a freight yard immediately south of 72nd street: freight service lasted at least until the late 1970s.
The last time I was in New York (ca. 5 yrs ago) the ruinous remains of the docks for NY Central car float traffic were still visible at the bank of the river about 71st street; my guess is that this preserved locomotive is near there. (In the 1970s I would occasionally go to the extreme west end of 71s street to look for railroad activity: there was sometimes a switcher parked around here, so it's not an inappropriate place to put a display locomotive! Of course, the only moving trains you'll see here are Amtrak's Empire Service: tracks are under Riverside Park but above ground and visible for a few blocks south of 72nd Street. If the photo is taken where I think it is, the Amtrak track is between the foreground locomotive and the background buildings.)
Go, check it out. An effort has been made to transform much of the old railroad yard here into park/recreational area: at the very least it's a pleasant place to walk on a summer afternoon.