The outhouse of my youth was a two-holer and rustic. Located near a large cottonwood tree and about 100 feet from the house, the little house faced a large field to the south. I remember that it always contained spiders and their webs.
The farmhouse had a room designated for a bathroom, but it was not plumbed until I was probably five years old. I don't know exactly when the outhouse was retired, but I do remember "playing school" in the room that eventually became the bathroom in the house.
Update: May 14, 2013
I found a letter, dated March 13, 1957, that my oldest sister wrote to a friend. Obviously, the letter was never sent, but she wrote, "We finally got our bathroom in the house and built a new Grade A barn. We are milking fourteen head and plan to be milking thirty-five head by summer."