Sierra Railway no. 3, (The engine that was responsible for the recording), in her Golden Years.
This sound effect can be found on Freesound.org. It is an extended version of TRAIN, WHISTLE - STEAM WHISTLE. The whistle is from Sierra Railway #3’s Petticoat Junction 3 chime whistle, and another locomotive or someone currently has that whistle since Sierra Railway #3 now owns a different whistle. Originally a Filmways Productions effect. It shouldn't be confused with James Whistle.