Custer National Forest is made up of small pockets of timbered buttes and grasslands scattered across three states--Montana, North Dakota, and South Dakota. It has been described as "islands of green in a sea of rolling prairie." It's southwest section is one of the gateways to Yellowstone National Park, and as such is part of the greater Yellowstone area, one of the largest intact temperate ecosystems left on the planet.
Granite Peak, the highest point in Montana, is contained within the Forest. Beartooth Scenic Highway, usually open May through September, crosses the mountain country. Hikers enjoy the region, but trail information, which can be obtained from US Forest Service offices, should be checked and updated before attempting any entry into wilderness areas.