The Middle Rockies ecoregion is characterized by steep, high-elevation mountain ranges and intermountain valleys. This is a disjunct ecoregion composed of three separate geographic areas, together which covers approximately 34,881 square miles. These three geographic areas are located in four states of Idaho, Montana, Wyoming and South Dakota, each of which are bordered by several different ecoregions.

The Western Area includes the Yellowstone area in northwest Wyoming, southwest Montana, and eastern Idaho. The Western area abuts the Great Plains (4C) and the Northern Rockies (3F) Ecoregions and the Foothills and Plains (5C) Ecoregion to the north. To the east is the Northern Great Plains (4C) ecoregion. To the south and west is the Snake River Basin (2H) ecoregion. To the south and east is the Wyoming Basin (3H) ecoregion.

The Middle Area includes the Bighorn Mountains in north-central Wyoming and south-central Montana. The Bighorn Mountains area lies between the Wyoming Basin (3H) Ecoregion to the west and the Northwestern Great Plains (4C) Ecoregion to the east and north.

The Eastern Area includes the Black Hills in western South Dakota and eastern Wyoming. The Black Hills area is entirely surrounded by the Northwestern Great Plains Ecoregion.

The Continental Divide crosses into this ecoregion the north of Montana, then along the Montana-Idaho border until it enters Wyoming and Yellowstone National park, where it traverses in a southeast direction and exits the park into the Teton Wildernes. Then the divide continue in a southward direction, then southeast again across the Wind River range, then over South Pass for a short distance until the divide leaves the South Rockies ecoregion and enters the Wyoming Basin ecoregion when it skirts around the Great Divide Basin.

On both sides of the divide, topographic relief causes local climate variability, particularly the effects of aspect, exposure to prevailing wind, thermal inversions, and rain-shadow effects, that are reflected in the wide variety of flora and fauna within the ecoregion.

The climate of the Middle Rockies ecoregion lacks the strong maritime influence found in the Northern Rockies (3F). Many mountain-fed, perennial streams occur and differentiate the intermontane valleys from the Northwest Great Plains (4C).

Mountains have Douglas-fir, subalpine fir, and Engelmann spruce forests, as well as some large alpine areas. Pacific tree species are not dominant and forests often have open canopies. Foothills are partly wooded or shrub and grass covered. Intermontane valleys are grass covered and/or shrub covered and contain a mosaic of terrestrial and aquatic fauna that is distinct from the nearby mountains.

Common land uses include: recreation, logging, mining, and summer livestock grazing.

Custer State Park

Black Hills National Forest

Crazy Horse

Jewel Cave National Monument

Mt. Rushmore National Memorial

Wind Cave National Park

Breezy Point Viewpoint (43.889905, -103.475661)

China Wall (44.3383922, -103.6517251)

Mammoth Site Museum (43.424197, -103.484142)

Wonderland Cave (44.273960, -103.501216)

Evans Plunge Mineral Warm Springs (43.441040, -103.480417)

Skyline Drive, Rapid City, SD