Over 200 miles in length, the Bighorn Mountains stretch from north-central Wyoming into southern Montana. This range, which angles southeast to northwest, rises between the Bighorn Basin to its west and the Powder River Basin to the east. The Bighorn River drains the west side of the range, cutting a scenic canyon through its northern tip on its way to join the Yellowstone River. The famous Little Bighorn River rises on the northeast flank of the range, the Tongue River drains its central east side and the upper tributaries of the Powder River head along the southeast slopes of the range.
An outlier of the Rocky Mountain Chain, the Bighorns formed during the Laramide Orogeny, 70 million years ago, as ancient Precambrian rock crumpled upward through the overlying Paleozoic and Mesozoic sediments. Precambrain granite is exposed along the crest of the range, which is generally 11-12,000 feet above sea level, while metamorphic Paleozoic rocks are exposed across the mid-elevation flanks and Mesozoic sedimentary rocks adorn the lower mountain slopes and foothills. Cloud Peak, 13,167 feet, is the highest point in the Bighorns, surrounded by the 189,000 acre Cloud Peak Wilderness Area in the southern portion of the range; it is classified as an ultra-prominent peak, rising 7067 feet above the lowest topographic contour that encircles it without including a higher summit. Prominence correlates with the extent of a summit's unobstructed vistas and Cloud Peak has the 15th greatest prominence in North America (second only to Gannett Peak in Wyoming).
Relatively undeveloped and isolated from large cities, the Bighorns appeal to naturalists and back-country enthusiasts. Joining the usual mix of western mountain birds and small mammals are black bear, mountain lions, elk, moose and mule deer; pronghorn are also found on the lower slopes and adjacent plains. Grizzly bears once inhabited the Bighorn Mountains but were extirpated by the mid 20th Century.
