Re: Photo: Unloading Can Stock (1948)
I'm also a little late to the party on can loading in boxcars. The Ahnapee & Western in Wisconsin had customers that received cans in bulk. Evangeline Milk Company produced condensed milk for First National Stores in Boston, Mass. In our era, they received carloads of baby vent-hole cans from Weirton, WV that were loaded in bulk rows and unloaded with the 'rakes' that Doug mentioned. The cans rolled down a 'rollway gravity conveyor' into a lift that brought them up into the can loft where they would be added to the canning line and fed by gravity. See attached image of unloading.
The cherry canneries in Sturgeon Bay received cans differently. Theirs were loaded in bags in the car, and unloaded mostly via team tracks into trucks for delivery to the offline canning plants. Evangeline Milk would sometimes receive bagged cans also, and they later sourced from can plants nearer than WV.
See some sample waybills from the mid-60s here: