Continental Divide

The Continental Divide — also known as the Great Divide — is one of the defining geographic features of Colorado, running in a serpentine course along the crest of the Rocky Mountains from the Wyoming border in the north to the New Mexico border in the south. It is a geologic crest running through Colorado's Rocky Mountains, with rivers on the west slope draining into the Pacific Ocean and water on the east slope draining into the Atlantic. More than merely a topographic line on a map, the Divide shapes the state's climate, hydrology, settlement patterns, and economy — and has drawn explorers, miners, engineers, and outdoor enthusiasts for centuries.

Geography and Physical Character

The Continental Divide of the Americas is the principal, and largely mountainous, hydrological divide of the Americas, extending from the Bering Strait to the Strait of Magellan and separating the watersheds that drain into the Pacific Ocean from those that drain into the Atlantic and Arctic Ocean, including the Gulf of Mexico, the Caribbean Sea, and Hudson Bay. Within the United States, the Divide crosses into Wyoming within Yellowstone National Park and continues southeast around the Great Divide Basin, through the Sierra Madre Range into Colorado, where it reaches its highest point in North America at the summit of Grays Peak at 4,352 metres (14,278 ft).

From north to south, the Great Divide in Colorado follows a serpentine path through Routt, Jackson, Larimer, Grand, Boulder, Gilpin, Clear Creek, Summit, Park, Lake, Eagle, Pitkin, Gunnison, Chaffee, Saguache, Hinsdale, San Juan, Mineral, Rio Grande, Conejos, and Archuleta Counties. The divide forms part of the boundaries of each county it touches.

Entering the top of Colorado from Wyoming, the Continental Divide stays above 10,000 feet and passes through mountaintops exceeding 12,000 feet, until dropping to 9,426 feet at Rabbit Ears Pass. The altitude and environment of the divide ranges from high alpine tundra at places like Grays Peak and the flanks of San Luis Peak (14,022 ft) to lower-elevation basins, such as the area just east of Rabbit Ears Pass at the southern end of North Park. In most parts of the state, the route of the divide is flanked by coniferous forests and inhabited by a variety of flora and fauna, including marmots, bighorn sheep, and elk.

Within the state, the area east of the Great Divide is generally referred to as the Eastern Slope — or the Front Range — while the area west of the divide is known as the Western Slope. The Rocky Mountains, which form much of the Great Divide, began rising over 70 million years ago due to tectonic activity, directing rivers toward either the Pacific or Atlantic Oceans.

Human History

Humans have relied on the high-altitude resources of Colorado's Great Divide for millennia. Beginning around 1400, Ute people lived and hunted along the divide, making seasonal treks across its many passes and forging trails that later became the routes of railroads and highways. Before modern settlers, tribes including the Utes undoubtedly crossed the divide in Colorado during the summer months, and many of their pathways through the Rocky Mountains pre-date the modern routes over the same mountain passes.

The first modern settlers and explorers to cross the Continental Divide did not come through Colorado. Lewis & Clark crossed the Continental Divide at Lehmi Pass in Montana in 1805, and the Oregon Trail crossed the divide over South Pass in Wyoming. The terrain over South Pass would be considered mild compared to any path over the divide in Colorado.

Tennessee Pass is an important pass historically. The area was explored by John C. Frémont and Kit Carson in 1845, as the nearby state historic plaque attests. Also at the pass is the Ewing Ditch, which was among the first trans-continental water diversions on record, and may be the oldest one still in use. Constructed in 1880, it extends for a mile up the side of Piney Gulch, capturing drainage that would otherwise go into the Colorado River, and moves it over the Divide where it drains into the Arkansas River watershed.

Many wagon roads were built over the divide during the late 1800s. Some of these were eventually turned into modern auto roads, including Highway 6, the predecessor to Interstate 70 and the Eisenhower Tunnel. Toll roads played an important role in Colorado's development, and many of today's mountain passes began as toll roads that were used by wagons to haul mining ore out of the Rockies.

In 1882, a toll road was built over Independence Pass, though traffic dropped off when the railroads reached Aspen a few years later. In the 1920s, the State of Colorado started maintaining the road as State Highway 82.

Hydrology and Water Diversion

Most of Colorado's water, provided by snowmelt, spills into the western side of the Divide, while most of the population is on the eastern side. This imbalance has led to water diversion projects that move water from one side of the Divide to the other, dating back more than a century, and include some of the largest tunneling projects in the country.

One historic dilemma the state faced was the fact that 80% of the state's water is on the Western Slope, but 80% of the people live on the Eastern Slope where thirsty cities and farms need water. By building a series of reservoirs, canals, and tunnels that go under the Continental Divide, trans-mountain diversions were created to send water east. Sixty to seventy percent of Colorado Springs' water arrives that way, and Denver and many other cities and towns along the Front Range are also heavily reliant on Western Slope water.

The Great Divide in Colorado is the source of the Colorado, Rio Grande, and Arkansas Rivers, three of the continent's most important waterways. It also contains headwaters of the Colorado River's major tributaries, such as the Gunnison and San Juan Rivers.

In 1922 the state legislature passed a bill to create a 6.2-mile tunnel through the Great Divide for the Denver, Northwestern & Pacific Railway — a project long planned as part of businessman David H. Moffat's rail line, nicknamed the Moffat Road. The Moffat Tunnel, as it came to be known, was completed in 1928, with its east portal located along South Boulder Creek west of Rollinsville and its west portal located in Winter Park.

Between the 1930s and 1950s, the Colorado–Big Thompson Project was completed, bringing water from the Colorado River on the Western Slope to thirsty farms and cities along the Front Range. The lynchpin of the project is the Alva B. Adams Tunnel, bored through the Continental Divide under Rocky Mountain National Park. Water passes through the tunnel on its way to a labyrinth of reservoirs, canals, and ditches along the Front Range.

The rivers may flow to the east and west on their respective sides of the Continental Divide, but thanks to human engineering, some of the rain that falls on the western side of the divide in Colorado crosses over the divide at least once before heading to its destination on the eastern side. In the section of the divide near Jones Pass and Berthoud Pass, the water crosses the divide three times before finally heading out of the mountains, passing through the Gumlick Tunnel, then the Vasquez Tunnel, then the Moffat Tunnel.

Mountain Passes

There are a total of 15 paved mountain passes that cross the divide in Colorado. These passes have served as critical corridors for Native American travel, mining operations, rail lines, and modern highway traffic alike.

Independence Pass, the second highest paved crossing of the Continental Divide, is located ten miles south of the mostly disused tunnels of Hagerman Pass. The highway continues west to Aspen, and is active with biking and tourists. The modern highway is closed for half the year because of snow, though the old toll road was kept open year around.

Loveland Pass and Berthoud Pass are two of the most prominent crossings in the northern part of the state, used by generations of travelers and skiers. The Eisenhower Tunnel also goes through the divide, providing a year-round passage under the Divide at an elevation of approximately 11,000 feet on Interstate 70 and standing as a major engineering achievement of the 20th century.

Just 20 minutes south of Breckenridge, Hoosier Pass sits at 11,542 feet and offers stunning views of the Mosquito Range. A parking area at the summit makes it an easy stop, and visitors can walk a short distance to stand directly on the divide.

The twentieth century saw the Great Divide's status as a great barrier somewhat diminished, as Coloradans and the federal government used new technology and advanced engineering to bore through its granite flanks and create tunnels for rails, roads, and water.

The Continental Divide National Scenic Trail

Established by Congress in 1978, the Continental Divide National Scenic Trail (CDT) spans 3,100 miles between Mexico and Canada, traversing five states and connecting countless communities along the spine of the Rocky Mountains. Colorado holds a substantial share of this iconic route.

The entire Continental Divide Scenic Trail is 3,100 miles long, 740 of which reside in the state of Colorado. The CDT in Colorado is dominated by the sharp, tall spine of the Rockies. The average elevation of the trail in Colorado is 10,000 feet above sea level, and along the way it summits the highest peak on the Continental Divide — and also the highest elevation of any National Scenic Trail — Gray's Peak, a stunning 14,270 feet above sea level.

The alpine tundra and high-elevation pine forests of Colorado are home to mountain goats, coyotes, pikas, black bears, and elk. Heading north from the border with New Mexico, the CDT soon enters the Weminuche Wilderness, Colorado's largest designated wilderness area, situated in the Rio Grande and San Juan National Forests. This 100-mile section of the CDT is known for its ruggedness and isolation, and presents a thrilling and rewarding challenge for hikers.

The establishment of the Appalachian Trail and the Pacific Crest Trail inspired proposals to create a Continental Divide Trail. The first section of the proposed trail was laid out in Colorado in 1962 by the Rocky Mountain Trails Association. In 1965, President Lyndon Johnson proposed a national system of trails, and in 1968 the U.S. Congress adopted the National Trails System Act. In 1978, the Continental Divide Trail was formally established with the responsibility for management given to the U.S. Forest Service.

Ranging from 4,000 to 14,000 feet, the CDT provides a variety of recreational activities to hundreds of thousands of people each year, including hiking, horseback riding, cross-country skiing, snowshoeing, wildlife viewing, fishing, hunting, sightseeing, mountain bicycling, backpacking, and more. Thru-hikers of the Continental Divide Trail, the Appalachian Trail, and the Pacific Crest Trail achieve what is known as the Triple Crown of Hiking. The 740 miles of the CDT in Colorado offer ample hiking and backpacking opportunities along the Continental Divide, with the route broken out into nine segments, each of which provides its own unique opportunity.

Grand Lake and Winter Park serve as key gateway communities to the Continental Divide Trail, offering hikers and adventurers direct access to one of the nation's most iconic long-distance routes. Steeped in mountain history and hospitality, these towns have long welcomed CDT travelers with trail access, lodging, supplies, and a true sense of Colorado's high-country character.