The Little Free Library movement started in 2009 when Todd Bol from Hudson, WI, built one in the shape of a one-room schoolhouse in honor of his mother, a retired teacher.  Now more than 1000 have sprung up like mushrooms around the country and overseas. Wisconsin, though, remains the hotbed of Little Free Libraries. 

For more information take a look at the Little Free Library website.  http://www.littlefreelibrary.org/