This image shows a couple of the private docks extending out from the Des Moines beach area of West Okoboji Lake. Tied up at the closer dock is an excellent example of a wooden pleasure boat from the 1940s.
The L.L. Cook Co., Milwaukee, WI
Docks such as these were commonly built by owners of lakefront property as well as being built and operated by resort and campground owners. This picture dates from the 1940s.