I do a fair amount of canning, and that is an impressive bit of work there. They must have a very large family or they are canning for neighbors as well.

At that time, if you didn't have a pressure canner, it was considered safe enough to use a "hot water bath" to can vegetables. Jars of non-acid vegetables would need to be placed into a boiling water pot and boiled for up to an hour and a half to kill all the botulism spores that otherwise grow on sealed veggies.

My dad's older cousin mentioned once about his mom canning in August, boiling the jars in a double boiler on the range, with the steam all but peeling the wallpaper off the walls. And you couldn't open a window or a door to get a breeze because it was thought that the cooler air would cause the jars to break after canning.

Prior to the general use of pressure canners to process non acid vegetables (like green beans) there were the occasional tragedies of entire families dying from botulism poisoning. Around here, green beans were considered especially risky.

So, buy a pressure canner if you want to can corn or beans or okra, or anything like that!

I count at least 720 jars, split between quarts and half-gallons. That's an average of 48 ounces per jar, or 34,560 ounces. Divided by 16 you get 2,160 pounds of food. It takes a lot of work to grow and harvest a ton of food by hand.