The Y's are locations of turning wyes. I assume P is for Phone, but I suppose it could be passenger. O is a curiosity. Maybe it is oil as in valve oil and journal oil as S.Baker was the main engine terminal and location of the railroads stores warehouse. If I typed LDL, it was a mistake and should have been LCL for "Less than Car Load". Up to at least sometime in the 60's railroads carried mixed freight in box cars which the agents had to sort out and call customers to pick up, or the rr would deliver it by their own depot hack or freight truck. I know our business used to receive white appliances this way with the local UP depot having a small truck to make deliveries. The box car that these 2 or three crated appliances came in might have tractor tires for the local coop, a pallet or two of hardware for one of the local stores, a crated band saw blade for the mill, you name it.