When did railroads start using diesel engine block heaters?

[Puddlejumper]

Thanks for the info. I'm modelling a New England short line in 1979 and am trying to decide if I can fit an engine house on the layout.. I might forgo the engine house so that I can fit an aggregate company in there.

I imagine a small short line might put antifreeze in the radiator, since it would be economical to do so. The assumption could be that the engine house is on the unmodeled portion of the railroad. Or a small spur, with a crew shack (with wood stove), small tool house, and electric cord to plug in the loco when not being used. Sounds quite justifiable to me.

Dave