There's a whole genre of linen postcard comics from the 1940s and 1950s. Much of the humor would be considered completely polictically incorrect today. There are entire blogs devoted to this type of postcard (see Postcard Funnies, as one example). The themes range from male/female relations to life in the military, from hillbillys to fat people, and a whole range of subjects in between. The Mystery Sender sent these two, and often sends these types of cards (along with several featuring Mt. Hood).
One of the recurring themes I've noticed is the outhouse and all its attendant history and complications. I suppose outhouses still exist, but they've mostly been replaced by port-a-potties and a variety of fancier buildings. For a history of the outhouse, click here. For more funny outhouse postcards, click here.