COColorado Geography

The lowest ground in Colorado sits at 3,315 feet, a point on the Arikaree River in Yuma County where the water slips across into Kansas. That number is higher than the summit of the highest point in eighteen other states. Nothing here is remotely near sea level. Average elevation across the whole state runs around 6,800 feet, the greatest of any state, and the vertical distance from that Kansas line to the top of Mount Elbert is 11,125 feet.

Four physiographic provinces inside one rectangle

Roughly the eastern two fifths of Colorado belongs to the Great Plains, a gently tilted apron of sediment shed off the mountains. At about the line of Interstate 25 the Front Range breaks out of that apron with almost no foothill transition, which is why Denver, Boulder, Colorado Springs and Pueblo all sit in a single north to south string against the wall.

West of the crest the Southern Rocky Mountains province gives way to the Colorado Plateau, all mesas, canyons and horizontal sandstone. Grand Mesa near Grand Junction is a basalt capped tableland of roughly 500 square miles, and the Black Canyon of the Gunnison cuts a slot so narrow that parts of the inner gorge get half an hour of direct sun a day. Its Painted Wall rises 2,250 feet, the tallest cliff in the state. A fourth province, the Wyoming Basin, reaches down into the Sand Wash country of the northwest corner.

The San Luis Valley is the odd one. It is the floor of the Rio Grande Rift, a flat high desert basin at about 7,500 feet ringed by the San Juans and the Sangre de Cristos. Wind pushes sand off the valley floor against the Sangre de Cristo wall, where it piles into the Great Sand Dunes, roughly 750 feet from base to crest and the tallest dunes in North America.

Mount Elbert, and the fourteener arithmetic

Mount Elbert in the Sawatch Range reaches 14,440 feet. It is the highest summit anywhere in the Rocky Mountains, on either side of the Canadian border, and the second highest in the contiguous United States, about 65 feet shy of Mount Whitney. Mount Massive stands next to it at 14,428, giving Colorado the second and third highest peaks in the lower 48 within sight of each other.

Counting peaks above 14,000 feet depends on the rule used. Apply the standard 300 foot prominence test and the total is 53. Include subsidiary summits that climbers treat as separate objectives and the count reaches 58. By either method Colorado has more than the rest of the contiguous United States combined. Pikes Peak, at 14,115 feet, is not among the tallest, but Katharine Lee Bates wrote the lines that became "America the Beautiful" after reaching its summit in 1893.

Leadville sits at 10,152 feet and is the highest incorporated city in the country. Denver earned its nickname on the thirteenth step of the state capitol, where a brass marker reads exactly one mile above sea level.

The headwaters state

Colorado is where a remarkable share of western water begins. The Continental Divide runs about 700 miles through the state, entering from Wyoming and leaving into New Mexico, and it splits the drainage between the Pacific and the Atlantic.

• The Colorado River starts at La Poudre Pass, 10,175 feet, inside Rocky Mountain National Park, and eventually reaches the Gulf of California.
• The Rio Grande rises in the San Juan Mountains and runs south through the San Luis Valley toward New Mexico and the Texas border.
• The Arkansas River begins near Leadville and carves the Royal Gorge, 1,250 feet deep, before reaching the plains at Canon City.
• The South Platte gathers in South Park, and the North Platte in North Park, both eventually feeding the Missouri and the Mississippi.

Because so much water originates here and so little arrives, Colorado is bound by nine interstate compacts telling it how much must be allowed to leave. Roughly half a million acre feet a year gets moved the other way, from the wet western slope to the dry populated east, through tunnels bored under the divide. The Alva B. Adams Tunnel runs 13.1 miles beneath Rocky Mountain National Park to do exactly that.

A rectangle on paper, a jagged line on the ground

Congress defined the Territory of Colorado in 1861 with pure coordinates: the 37th and 41st parallels north, and meridians 25 and 32 degrees west of Washington, which correspond to 102 degrees 03 minutes and 109 degrees 03 minutes west of Greenwich. Four degrees of latitude by seven of longitude, no rivers or ridges involved.

Surveyors then had to put that abstraction on the ground with chains and transits between 1868 and 1879, working in country where crews approaching from opposite directions rarely met exactly. The marked boundary steps sideways at many points where one traverse failed to close on the next, so the tidy rectangle on a map is a simplification of a line with a great many small corners.

At the southwest corner sits the Four Corners monument, the only place in the United States where four states meet at a single point. The 1875 survey put the marker several hundred feet east of where 109 degrees 03 minutes actually falls, and courts have consistently held that the monument as placed, not the theoretical coordinate, is the legal corner. Colorado shares real boundary length with six states and touches Arizona at nothing more than that one point.

A 176 degree temperature range

The hottest reading ever taken in Colorado is 115 degrees Fahrenheit, at Las Animas on July 1, 1933, matched at John Martin Dam on July 20, 2019. The coldest is minus 61, at Maybell on February 1, 1985. The 176 degree spread between them belongs to a state small enough to drive across in a day.

The mountains do the sorting. Eastern plains towns average around 15 inches of precipitation a year, semi arid by any measure, while the San Juans catch storms head on and Wolf Creek Pass collects more than 400 inches of snow in a typical winter. Alamosa, on the San Luis Valley floor at 7,544 feet, gets a growing season under 90 days despite sitting at the same latitude as coastal California. The Front Range corridor lies inside the belt sometimes called Hail Alley, where seven to nine hail days a year make it the most hail prone populated area in the country.

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