Lake Duluth was a proglacial lake that formed in the Lake Superior drainage basin as the Laurentide ice sheet retreated. The oldest existing shorelines were formed after retreat from the Greatlakean advance, sometime around 11,000 years B.P. Lake Duluth formed at the western end of the Lake Superior basin. Lake Duluth overflowed south through outlets in Minnesota and Wisconsin at an elevation of around 331 m ASL.
The drawing on this page is accurate but uses the obsolete term, "Valders". Valders was replaced by the term "Greatlakean" when stratigraphic problems forced Valders to be abandoned.