I love good pictures of Knott's from the 1950's!
Here's a rare look at the old round house. I'm no expert, but something tells me that this building isn't actually round. It looks appropriately ancient, though it couldn't have been more than about 4 years old (track was being laid for the railroad in 1951). Just think how nice and cool it must have been inside during the summer months! I can only assume that a different structure is now used for housing and refurbishing the trains; if anybody has details, I'd love to hear them!