The majority of the Forest lies in eastern Idaho and the remainder in western Wyoming. Situated next to Yellowstone and Grand Teton National Parks, the Forest is home to a diverse number of wildlife and fish, including Threatened and Endangered species, wilderness, scenic panoramas and intensively managed forest lands.

The Forest lies almost entirely within "the Greater Yellowstone Area" or "the Greater Yellowstone Ecosystem," an area of 12 million acres and the largest remaining block of relatively undisturbed plant and animal habitat in the contiguous United States. The area continues to gain prominence for its ecological integrity. The United Nations has identified the area as a Biosphere Reserve.

On a larger scale, the Forest lies along the Continental Divide, at the uppermost reaches of the Columbia River Basin, an ecosystem of 40 million acres extending from Western Washington to the Southeastern Idaho border and encompassing parts of Montana, Wyoming, Nevada and Utah. The Forest includes all or portions of several distinct mountain ranges, including the Lemhi, Beaverhead, Bitterroot, Centennial, Henry's Lake, Teton, Big Hole, Caribou, and Snake River Ranges. Elevations range from near 5,000 feet on the Snake River to over 12,000 feet on the Forest's western and easternmost reaches. The Forest contains the Island Park Caldera and several reservoirs. Topography ranges from rolling foothills to rugged, glaciated mountain peaks. Although most of the land is dry and semi-arid, 190 stream headwaters situated on the Forest provide varied vegetation to support a multitude of uses. The area has cold, moist winters and hot dry summers. Average annual precipitation, most of which falls as snow, increases with elevation. As little as ten inches of precipitation falls in lower valleys and as much as forty inches occurs at the highest elevations. Wide temperature extremes exist, with summer temperatures at lower elevations exceeding 100 degrees Fahrenheit and winter temperatures at higher elevations falling to less than 40 degrees below zero Fahrenheit.

In recent years the Forest Service has embraced the concept of ecosystem management. This is an approach to natural resource management that strives to ensure healthy, productive, sustainable ecosystems by blending the needs of people and environmental values on a given area such as the Targhee National Forest. An ecosystem is a complex system of living and nonliving components that interact and change continually. Healthy ecosystems are those that retain all of their parts and functions for future generations even though vegetation patterns, human uses, or other conditions may change. Understanding ecological processes (fire and other natural disturbances) and how these processes shaped vegetative patterns over time in a landscape are important steps towards implementing ecosystem management. Many resources are described using the ecological units known as subsections (also referred to as management areas). These units exhibit unique patterns in soils, landform, topography and potential natural vegetation, among other characteristics. The Forest encompasses part or all of seven subsections:

* Lemhi/Medicine Lodge
* Centennial Mountains
* Island Park
* Madison Plateau
* Teton Range
* Big Hole/Palisades Mountains
* Caribou

Wilderness
In October 1984 the Wyoming Wilderness Bill was signed into law creating the Jedediah Smith Wilderness (116,535 acres) and the Winegar Hole Wilderness (10,820 acres) on the Targhee National Forest. The Wilderness Act allows hiking, camping, hunting, fishing, skiing, and grazing in these areas. Fires are allowed in most areas, but some areas are closed to open fires to protect resources. Special regulations are issued by Ashton and Teton Basin districts. Motorized or mechanical equipment is prohibited. Horses can be used in both Wilderness areas; however, overnight camping with stock is not allowed in specified locations. The Jedediah Smith Wilderness is on the west side of Grand Teton National Park. The towns of Victor, Driggs, Tetonia, and Ashton, Idaho are 5 to 20 miles west of the Wilderness. The Winegar Hole Wilderness is 25 miles east of Ashton, Idaho and adjacent to the southeast corner of Yellowstone National Park.

Forest Renewal
The Targhee National Forest is an old forest becoming new. In the 1960's, timber on the Forest was primarily old growth lodgepole pine interspersed with Englemann spruce, subalpine fir, and Rocky Mountain Douglas fir. The condition of the lodgepole pine caused an epidemic of mountain pine bark beetle that destroyed the lodgepole. During the 1960's and early 1970's, Forest managers tried several methods to halt the advance of the bark beetle, but none of them were economically feasible or successful.

The dying trees interfered with effective management of other Forest resources and created a fire hazard from the build up of dry fuel. In 1974, Targhee Forest managers implemented a salvage program designed to use the deadwood and open large areas to reforestation. The wood was sold in commercial and personal use firewood sales, in small sales for posts and poles, and in larger sales for use in making pressed board.

Salvage and reforestation went hand in hand. As soon as areas were cleared of dead trees, new trees were planted. Lodgepole was combined with other native varieties too produce a healthy mixture of species. Diversification of tree species and age affords protection against recurrence of the devastating epidemic.