Superior Upland

For purposes of description, the physical geography of the United States is split into several major physiographic divisions, three of which being the Laurentian Highlands, Interior Highlands and the Interior Plains (see subdivisions 1 and 11–15) lie in the interior of the U.S.

The Superior Upland is the province of the Laurentian Upland which projects into the United States west and south of Lake Superior. This upland, part of the Canadian Shield along with the Adirondacks, is a greatly deformed structure and is composed primarily of igneous and metamorphic crystalline rocks commonly associated with a rugged landscape. At some prehistoric period, this had a strong relief, but today the upland as a whole is gently rolling with the inter-streams surfaces being plateau-like in their evenness. Here they have altitudes of 1,400 to 2,300 feet (700 m) in their higher areas, such as the Misquah Hills and Huron Mountains. In this province, we find a part of those ancient mountains regions that were initiated by crustal deformation and then reduced by a long continued erosion to a peneplain of modern relief. A peneplain with the occasional moderately high monadnocks left behind during the peneplanation of the rest of the surface. The erosion of the region must have been far advanced in prehistoric times, even practically completed, because the even peneplain surface is overlapped by fossiliferous marine strata from an early geological date, Cambrian. This shows that the depression of the region beneath an ancient sea took place after a long existence as dry land.

...
Wikipedia