Sophie told me about these tiny Lake Mendota houses in Middleton. After a bit of digging, I found this piece by Valeria Davis-Humphrey from the Wisconsin State Journal (June 9, 1997): 

It was in June 1898 that a group of fishermen received a land grant from the state of Wisconsin for a place to moor their boats. These men chartered the nonprofit Middleton Boat House Co. and distributed shares among themselves. Each share was worth 6 1/2 feet of shoreline just north of the current Middleton Beach Road…. 

The fishermen would roll their boats across logs up onto the shore, where they stored them in squat huts, or boathouses. One by one, owners secured second shares and began building larger shelters — a whopping 12 feet wide. Her uncle was the fourth owner to build a second level on his boathouse, where he could clean fish or stay overnight.

Condominiums have replaced the marina that used to be across from the main pier, but the boathouses have deliberately remained much the same. Even though they now are on the city’s water and sewer system, the houses only have glorified indoor privies and are still unsuitable for year-round living.

They’ve never had addresses. So if visitors get turned around, they’re just plain lost in a row of 20 unnumbered boathouses.