The range has an area of about 15,000 square miles (39,000 km2), stretching east and southeast of Pendleton, Oregon, to the Snake River along the Oregon–Idaho border.

[6] The Blue Mountains are unique as the home of the world's largest living organism, a subterranean colonial mycelial mat of the fungus Armillaria ostoyae.

[13] Geologically, the oldest rocks of the Blue Mountains (400+ to about 150 million years in age) were created as island arcs in the Pacific Ocean and accreted onto the North American plate.

The Wallowa Mountains are considered to be part of the Blues by many geologists because their geology includes the same accreted terranes as the Elkhorns, Greenhorns, and Strawberries, although their mechanism of uplift differs somewhat.

The southern portion of the Blue Mountains were inhabited by several different bands of the Northern Paiute, a Great Basin culture.

[16] The Natives used to purposefully burn small parts of the forest in order to create pastures to attract game for hunting.

U.S. Route 26 crosses the southern portion of the range, traversing the Blue Mountain Summit and reaching an elevation of 5,098 feet (1,554 m).

Birds of the area include bald eagle, Lewis's woodpecker, Williamson's sapsucker, red-breasted nuthatch, golden-crowned kinglet and many migratory species, with the riverbanks important habitat for this birdlife.