[6]: 25–28  Above Carlton travelers proceeded upstream through quieter stretches to the location of Floodwood, Minnesota, where they turned southwest up the sluggish East Savanna River in the bed of Glacial Lake Upham.

Coming to a small rise, the travelers commenced the portage, which in its eastern reaches was marshy, mosquito-infested, and among the most unpleasant and tortuous of all the routes taken by the voyageurs.

[12]: 61–63  In times of low water, the portage was drier but the river became too shallow for canoes, so voyageurs would continue to hike overland to the northeast bay of Big Sandy Lake.

Some went no further than the American Fur Company's large regional trading post on Big Sandy Lake operated by William Aitkin in the 1820s and 1830s, the years of peak usage of the route.

[12] When the Northern Pacific Railroad, building west from Duluth reached nearby McGregor in 1870, the portage fell out of use for through traffic,[12] but continued to be used for local trade and access to the interior.

[11] Activities include summer and winter camping, hiking, snowshoeing, and ski touring on the old portage and other trails, mountain biking, and snowmobiling, as well as swimming, fishing, canoeing, and boating on Loon Lake.

[9] Named for its open marshy grassland, the park's peat bogs and marshes include sedges and black spruce, tamarack, and white cedar.

[8][9] Land animals in the area include moose, black bears, deer, timber wolves, coyotes, skunks, amphibians, and wood turtles.

Birds include bald eagles, sharp-tailed grouse, warblers, boreal owls from Canada which winter in the area, sandhill cranes, trumpeter swans, and loons.