This ecoregion extends from Wawa, Ontario, in the west to just past the Ottawa River in the east. The ecoregion is marked by warm summers and cold winters. The mean annual temperature is approximately 3°C. The mean summer temperature is 15°C and the mean winter temperature is -9°C. The mean annual precipitation ranges 800-1000 mm, although it exceeds 1000 mm along the shores of Lake Superior. This ecoregion is classified as having a humid mid-boreal ecoclimate. Its mixed forest contains some areas of deciduous forest along the east shore of Lake Superior between Sault Ste. Marie and Wawa, and is characterized by white spruce, balsam fir, and eastern white pine, along with some red pine, yellow birch, and trembling aspen. Warmer areas along the Lake Superior shore contain sugar and red maple, and yellow birch, whereas white, red, and jack pine occur on drier terrain. Black spruce, tamarack, and eastern white cedar dominate in poorly drained areas. The ecoregion is underlain by massive, crystalline, acidic, Archean bedrock, forming hummocky and undulating, broadly sloping uplands and lowlands. The Cobalt Plain in its eastern section is composed of flat-lying clastic sediments with ridges and hills formed by gabbro sills or granitic rock inliers. There is a significant amount of fluvioglacial deposits increasing southward. A large area of fine-textured lacustrine deposits occurs near New Liskeard, and an area of beach deposits near Chapleau. Bedrock outcroppings are common, and Humo-Ferric Podzols developed on discontinuous sandy materials are the dominant soil. Significant inclusions are Dystric Brunisolic soils found on the finer sediments around Chapleau, Gleysolic soils on the clays and loams of the Little Clay Belt near New Liskeard, and limited areas of Mesisols and Fibrisols on low-lying, poorly drained sites. Wetlands are characteristically bowl bogs that are treed and surrounded by peat margin swamps. Characteristic wildlife includes moose, black bear, lynx, snowshoe hare, wolf, coyote, and white-tailed deer. Bird species include the American black duck, wood duck, hooded merganser, and pileated woodpecker. The major land uses include forestry, mining, hydroelectric power generation, and recreation. The Little Clay Belt of New Liskeard supports livestock and grain farming. The major communities include Témiscaming, Wawa, Chapleau, Kirkland Lake, and Sault Ste. Marie. The population of the ecoregion is approximately 157 200.
This ecoregion is part of the Boreal Shield ecozone.