The outhouse, as we know it, originated in Europe more than 500 years ago, in the fifteenth and sixteenth centuries. The finer inns began offering "his" and "hers" outhouses. But, because most people were illiterate, symbols were used on the outhouses to show which was "his" and which was "hers". Pictures of the sun and moon were the obvious choice. From ancient times, the "sun" had been a symbol of all that was masculine and the "moon" of all that was feminine. 

As time went by, innkeepers reasoned that maintaining a men's outhouse was unnecessary, because they could always go out in the woods--- and those who couldn't or wouldn't, could use the women's outhouse. Men's outhouses disappeared, leaving only women's outhouses, marked with the crescent moon.

Outhouse Facts & Trivia
With permission from legendsofamerica.com/WE-Outhouse2.html

Outhouses With Two Holes:  No, these old vintage structures weren't usually doing double duty.  Rather, most contained two holes of different sizes - one for adults and one for children.  Don't think those kids wanted to sit on the bigger hole and risk the consequences.  However, that being said, some large families would have multiple holes for use at the same time.  In Montana, there was once a hotel that had an outhouse with 12 seats. 

Crescent Moon:  The crescent moon cutout and the star cutout on the door of many outhouses goes back to Colonial times. In a time when few people could read, the crescent moon was the symbol for women while the star cutout was for men.  It is thought that the men, in general, let their outhouses fall into such bad shape that it was the women's outhouses that survived the test of time.  The cutout also let light into the outhouse as there were usually no windows.

Outhouse Builders:  During Roosevelt's Works Progress Administration - the WPA - there were teams of outhouse builders who built most of the outhouses in rural areas. 

Toilet Paper:  Considered a luxury by most rural families, newspaper or pages from old catalogs was more often used. 

Average Outhouse:  Usually they were 3 to 4 feet square by 7 feet high with no window, heat, or  electric light.  Due to the odor, most  were built between 50 and 150 feet from the main house, often facing away from the house.  So that didn't have to smell the unpleasant odor, many people left the door open  while they were using it.  Old-timers will admit that they had trouble breaking this habit with the invention of indoor bathrooms. 

Two Story Outhouses:  How in the heck did that work?  Well, the upstairs facilities were situated a little further back so that the "materials" released from the second floor would fall behind the wall of the first floor. There are a few of these old relics still around.  The one below was built next to a large store in Gays, Illinois.  The store has long since been torn down, but thanks to those fine citizens of Gays, the "skys-crapper" was preserved.

Thomas Crapper:  It is a myth that Thomas Crapper invented the toilet.  Though the man held several patents for plumbing related products, he did not invent the water closet.