When I was growing up in western Washington state (a long, long time ago -- some neighbors still had outhouses and didn't have electricity, yet) our grandparents, and aunts & uncles near us had outdoor canning buildings. Basically they were a small building, probably 16x20 or so, that had large screened windows, a roof, screen doors, a wood cook stove (with a water heater jacket), sink with hot & cold running water, lots of tables, and a propane cook stove.
I have many memories of helping to shuck peas, snap beans, turning the handle on the Foley Food Mill, etc., while all the family helped to put the garden's crops for the winter into jars. In the fall, during hunting season, we even did venison, elk and some beef into canning jars. All hot pack. My mom even made grape juice by canning a cup of slightly crushed grapes into a quart jar, filled with hot water and a little sugar, and then hot packed.
Lots of memories. Not sure I want to do it all again. No one had freezers yet. Some fresh veggies and fruit went into the underground root cellars and all of the jars of canned goods were locked up in the oversize water well pump house (same place we hung our beef or venison and elk because of the cool temperature. Our pump hour was actually very insulated and stayed pretty much the same temperature year around -- cold, but not freezing.