Crazy Mountain National Forest was established as the Crazy Mountain Forest Reserve in Montana by the U.S. Forest Service on August 10, 1906 with 234,760 acres (950.0 km2). It became a National Forest on March 4, 1907. On July 1, 1908 it was combined with part Yellowstone National Forest to re-establish Absaroka National Forest and its name was discontinued.
The forest is part of the Jefferson Division of Lewis and Clark National Forest. The Crazy Mountains are included in the unit, primarily in Meagher County.