Rabbit Ears Pass (el. 9426 ft, 2873 m) is a high mountain pass in the Rocky Mountains of northern Colorado in the United States, where U.S. Route 40 crosses the Park Range (Colorado). North of the summit is Rabbit Ears Peak which has the shape of rabbit ears, which displays two large columns of basalt rock formations from the second volcanic episode. Rabbit Ears Peak is underlain by a pink tuff and the basalt immediately to the west is underlain by red, vesicular ash. Volcanic breccia occurs only at the Peak, which is a large stratified breccia pile. The three basal layers are cut by a basalt dike immediately beneath the peak. The pass straddles the Continental Divide at the southern end of the Park Range. The name is taken from nearby Rabbit Ears Peak, a mountain in Jackson County, CO in the Park Range to the north that is prominently visible from the east side of the pass during good weather. The pass separates the upper basin of the Yampa River on the west from North Park and the upper basin of the North Platte River on the east. U.S. Highway 40 travels over the pass between Steamboat Springs and Kremmling; this is one of three crossings of the Continental Divide along the highway, along with nearby Muddy Pass to the southeast and the much higher Berthoud Pass closer to Denver.
The climate of Rabbit Ears Pass is generally semi-arid to humid. Vegetation consists mostly of pine, spruce, and aspen trees. Sagebrush grows on the Niobrara, Pierre and Coalmount formations. Undergrowth is dense in most places.
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This pass offers habitat to many different animal species. It supports important winter and summering ranges for many animals. Species commonly seen on the pass range from elk, mule deer, and moose, to black bears, foxes, long-tailed weasels, snowshoe hares, and a variety of bird species. The winter snowpack provides a seasonal habitat for many non-hibernating burrowing animals such as voles, lemmings, and shrews. The snowpack helps to make a subnivean zone, which is a porous material composed mostly of air acting as a reliable thermal insulator. There are boundaries set up to separate motorized use from foot traffic. These established boundaries decrease conflicts between users and seasonal closures related to snow depth and animal wintering ranges. Non-motorized recreation is permitted west of the pass and motorized recreation is permitted east of the pass. The boundary designating winter recreational usage on Rabbit Ears Pass provides an opportunity to study the influence of motorized recreation on the physical properties of the snowpack and animal use. This international bike competition takes riders up and over the pass descending into Steamboat Springs during end of a stage, and ascending over the pass during the beginning of the next stage. The pass also hosts the "Ride the Divide" Mountain bike race that takes place from Montana to Mexico every year. The trail over the pass begins at 10,038' (3060 m) at Base Camp Trailhead and ends at 9250' (2819 m) in the Medicine Bow National Forest, WY. The trail is 68.1 miles (99.5 km). This trail offers outstanding views east into North Park and west towards Utah. Users need to be prepared for weather extremes at all times.
Somewhat unusually, the highway over Rabbit Ears Pass has a gently rolling character in the vicinity of the summit. After crossing the Divide westbound, the road dips briefly and then reaches its highest point (about 9426 ft) before descending gently to the west summit (9400 ft) and then dropping steeply (6.8% N) toward Steamboat Springs. This is the 28th steepest pass in the State of Colorado.