The park is located on the divide between the watersheds of the Great Lakes and the Gulf of Mexico, both of which drain to the Atlantic Ocean. The area is a low-relief plain which was once a glacial lakebed. During the last phase of the Wisconsinan glaciation, the deteriorating continental glacier left behind connected lakes, known as Glacial Lakes Aitkin and Upham. Formed by the retreat of the Saint Louis Sublobe of the Superior Lobe of the glacier, Lake Upham drained through Lake Aitkin to the Mississippi River. The retreating glacier and the lakes deposited sand and sediments in the lakebed. As the lakes drained these sediments became the present plain.