The topography of the forest varies from rolling upland sites to extensive swamps in the southern and northeastern portion of the forest. The forest is divided between two watersheds: the Willow River and Lower Tamarack River along with the southern two-thirds of the forest, eventually feed into the St. Croix River, whereas, the numerous streams in the northern one-third portion of the forest lead to Lake Superior. The area's old-growth forest was logged throughout the nineteenth century, with the Willow, Tamarack, and Nemadji Rivers being used to drive logs down the St. Croix to sawmills in Stillwater. The majority of the forest came under the ownership of the state after tax forfeitures in the early 1900s.