This rock mound in the Menomonee River Valley near Milwaukee was discovered by Increase A. Lapham, Wisconsin's first scientist, in the 1830s. In 1862, James Hall was the first to recognize and interpret this and several other earby mounds as fossil reefs, making them the first ancient reefs described in North America and among the first described anywhere in the world. Thomas C. Chamberlin used this and other reefs in formulating his paleoecological and sedimentological model of reef development, which was published in his classic 1877 work, Geology of Eastern Wisconsin.

Information provided by the National Register of Historic Places, a program of the National Park Service.