Colorado

I

Introduction

Colorado, state in the western United States. The Rocky Mountains, or Rockies, form the most dominant physical feature of the state. To the west of the Rockies lie the high plateaus of the Colorado Plateau, and to the east are the Great Plains. High, rugged mountains and plateaus occupy fully two-thirds of the state and make Colorado a state of striking beauty. All of Colorado is more than 1,000 m (3,300 ft) above sea level. The state, with an average elevation of 2,070 m (6,800 ft), is the highest of all the states. The mountains and plateaus are rich in gold, silver, and other minerals and are the source of most of the state’s water. The mountains have played a major role in the development of Colorado, most recently by attracting a steady flow of tourists, but they have also been a barrier to travel, communication, and settlement. Except for small cities and towns in the sheltered river valleys and mountain basins, most of western Colorado is sparsely populated.

In contrast, eastern Colorado has flat, treeless plains that extend from the Rockies to the Nebraska and Kansas state lines. Cultivated where there is sufficient moisture or irrigation, they consist of croplands and grasslands. On the plains just east of the Rockies is Denver, which is the state capital, the center of the state’s largest metropolitan area, and a major city of the Western United States.

The state’s name, Colorado, is a Spanish word meaning “reddish colored.” It was the name early Spanish explorers gave to the Colorado River, which originates in the state. When Colorado became a territory in 1861, William Gilpin, the first territorial governor, formally requested that it be called by the old Spanish name. Colorado was admitted to statehood on August 1, 1876, during the 100th anniversary of the signing of the Declaration of Independence, and today its official nickname is the Centennial State.

II

Physical Geography

Colorado ranks eighth among the states in size. It has an area of 269,602 sq km (104,094 sq mi), including 974 sq km (376 sq mi) of inland waters. The state is rectangular in shape, measuring 623 km (387 mi) from east to west and 444 km (276 mi) from north to south. Colorado straddles the Continental Divide, which separates rivers flowing to the Pacific Ocean and the Gulf of Mexico. In Colorado the lands west of the divide are referred to as the Western Slope, while those to the east are often called the Eastern Slope.

---

---

A

Natural Regions

Colorado includes parts of three major physiographic provinces, or natural regions, of the western United States. They are, from east to west, the Great Plains, the Southern Rocky Mountains, and the Colorado Plateau. In addition, Colorado includes small sections of two other natural regions, the Wyoming, or Green River, Basin and the Middle Rocky Mountains, which lie in the extreme northwest. Both of these regions are, like the Southern Rocky Mountains, part of the vast Rocky Mountain System.

The Great Plains, a broad expanse of flat or rolling prairies that extend from Alberta to Texas, cover the eastern third of Colorado. They rise gently from about 1,200 m (about 4,000 ft) above sea level along the Kansas state line to about 2,100 m (about 7,000 ft) above sea level at the eastern foot of the Rocky Mountains. The plains are used mainly for growing wheat and other crops and for grazing cattle.

The physical features of the Great Plains are not uniform throughout the state. The plains are sometimes divided into three sections: the High Plains, the Colorado Piedmont, and the Raton section.

The High Plains, which include the most level land in the Great Plains, extend along the eastern border of Colorado. The only significant variations in relief occur where steep-sided river valleys, such as those of the Arkansas and Republican rivers, cross the plains or where there are shallow saucer like depressions.

The Colorado Piedmont, to the west of the High Plains, is more varied in relief, and many low ridges, steep bluffs, flat-topped mesas, and conical hills, called tepee buttes, rise above the surface. In the south the piedmont merges with the Raton section. The Raton section, more rugged than the Colorado Piedmont, includes numerous mesas and buttes of volcanic origin and narrow, rocky canyons.

The Southern Rocky Mountains occupy most of central Colorado and extend in a north-south direction across the state. In Colorado the Rockies are between 120 and 280 km (75 and 175 mi) wide and include 53 peaks with an elevation of more than 14,000 ft (equivalent to 4,267 m).

The mountains do not form a single highland area but are divided into two roughly parallel groups, or belts, of ranges. The mountain belts are separated from each other by several broad, high-altitude valleys and mountain basins called parks.

The eastern mountain belt includes the Laramie Mountains, the Front Range, and part of the Sangre de Cristo Mountains. The highest peaks of these eastern ranges are Blanca Peak, Longs Peak, and Mount Evans, all of which are more than 4,340 m (14,250 ft) high. Pikes Peak, a conspicuous landmark at the southern end of the Front Range, rises to 4,301 m (14,110 ft). Arapahoe Glacier, in the Front Range, is the largest glacier in the Southern Rocky Mountains.

In Colorado the Continental Divide, or Great Divide, follows the crest of the eastern mountain belt as far south as Mount Evans, then crosses over to the western belt and continues southward. The western belt of high mountains includes the Park Range, the Sawatch Range, and the San Juan Mountains. The Sawatch Range contains Mount Elbert, the state’s highest peak at 4,399 m (14,433 ft). The Sawatch Range and the San Juan Mountains combined contain 27 of the state’s mountains over 4,250 m (14,000 ft). The parks and valleys between the two mountain belts of the Southern Rockies are broad, relatively flat, grass-covered areas. The principal ones are, from north to south, North Park, Middle Park, South Park, and the San Luis Valley. They are separated from each other by spur ranges of the mountain belts that flank them. They vary from about 1,800 to 2,700 m (about 6,000 to 9,000 ft) above sea level.

The Colorado Plateau occupies most of western Colorado. It is made up of dozens of separate plateaus that range from about 1,500 to 3,400 m (about 5,000 to 11,000 ft) high and are arranged in seemingly haphazard tiers and groups. Many are separated or cut by deep canyons. Most of the canyons were formed by tributaries of the Colorado River, such as the Gunnison River. Rugged hills and a few mountain ranges rise from the Colorado Plateau.

B

Rivers and Lakes

On or near the Continental Divide rise headstreams or major tributaries of four great North American rivers, the Río Grande, the Colorado, the Mississippi, and the Missouri. The Río Grande rises in the San Juan Mountains and flows southward through the San Luis Valley into New Mexico. The Colorado rises on the western side of the Continental Divide near Longs Peak and flows in a southwesterly direction into Utah. Principal tributaries of the Colorado River that rise in Colorado are the Gunnison, Dolores, and San Juan rivers. East of the divide the chief rivers are the South Platte River, a tributary of the Missouri, and the Arkansas River, a tributary of the Mississippi. On the Arkansas River about 50 km (about 30 mi) southwest of Colorado Springs is the famous Royal Gorge, where the river makes its way eastward between red granite cliffs that tower 300 m (1,000 ft) above the water.

Although the rivers of Colorado are navigable only by small boats, they are important as a source of irrigation water for use in Colorado and adjoining states. However, the water level of the rivers fluctuates seasonally and from year to year. The level is generally low in winter and high in spring and summer, during the runoff of melted snow from the mountains.

Colorado has no large lakes of natural origin, but there are numerous small lakes in the mountains. The largest bodies of water in Colorado are the large reservoirs created by dams and used for irrigation and flood control. Among the largest are John Martin, Granby, Pueblo, and Blue Mesa reservoirs.