During the last Ice Age, four distinct, giant glaciers, originating in Canada, invaded what is now the northern United States. The last of these great ice blankets, called the Wisconsin Glacier, overrode much of Wisconsin. Around here, the Wisconsin Glacier slid over the old river valley that many geologists believe was the “Ancient Wisconsin River”. The glacier slid over these park lands, creating a wide terminal moraine only a few miles south and southwest of Lake Kegonsa. Thus, this park once lay under thick glacial ice.
As the glacier melted and retreated, its meltwaters carried vast amounts of sand, gravel and boulders into the old river valley, partially filling it. The melting ice also dropped huge loads of glacial rock and debris on the park lands.
The old valley, now dammed in places by glacial debris, holds the famous “4-Lakes” of the Madison area: Lakes Mendota, Monona, Waubesa and Kegonsa. This string of beautiful lakes has existed only during the last 12,000-15,000 years and is perched on glacial debris many feet above the old, buried valley floor. The present-day Yahara River connects the four lakes.
How Lake Kegonsa Got Its Name
Early area settlers referred to Lake Kegonsa as “First Lake” because it was the first of the four Madison lakes ”Kegonsa, Waubesa, Monona and Mendota” they encountered traveling north up the Yahara River.
The name Kegonsa is attributed to the Ho-Chunk (Winnebago) Indians who once lived in this area. Kegonsa means “Lake of Many Fishes” Today, Lake Kegonsa is still one of Wisconsin’s most productive fishing lakes.