Indeed it was, and one that would be near to the heart of most model railroaders for its almost-exclusive use of dingy industrial settings--Henry Spencer and the other characters of that world would look right on an industrial switching layout!
I'm thinking about doing a mini layout of a local metalworking facility--not a full steel mill (it was known as "Sacramento Pipeworks"), more of a local foundry, but extensive enough to cover two city blocks and have its own two-foot-gauge track (not sure yet what it was used for or if it actually had engines or was just for pushing heavy carts around) as well as being served by the SP.