The Natural Setting and Its Relation to Historic Development
History is concerned with the activities of people; it is the written record of human development within a given chronological period or geographical area. Important in the determination of a region's human activities are the influences of natural environment and resources. The effects of such factors as climate, geography, and geology on the development of human use and occupation find no better example than that of the history of southwestern Colorado. The opportunities offered in the land have formed the basis for social and economic growth in this region, yet have presented constraints and barriers to development as well. To chronicle the history of southwest Colorado, one must take the perspective of the geologist as well as the miner, the meteorologist and hydrologist as well as the farmer, the land-use expert as well as the rancher, and the topographer as well as the road engineer. The interpretation of southwestern Colorado's landscape has and continues to be a prerequisite for the region's development. The area's natural environment has been the foundation on which its inhabitants for many centuries have built a superstructure of human activities.  Over the period of prehistoric and recorded time, people of southwestern Colorado have valued different elements of their environment, and they have approached the natural resources of the area with changing ideas concerning the land's use.
The land formations of southwestern Colorado, its mountains, valleys, plateaus, and rivers, did not always look as they do today. During the many millions of years that have elapsed since the earth was formed, this area has undergone many geological changes. Great seas once covered the region, volcanoes poured forth shimmering streams of molten lava, glaciers formed and disappeared, and strange, fantastic plants and animals, never seen by man lived and died within its borders. 
The earliest rock formations of which we have knowledge are those called pre-Cambrian, produced perhaps as much as 2,000 million years ago. Some of these are igneous rocks, that is, rocks produced by volcanic action and deposited in a molten condition. Some are sedimentary rocks made up of material derived from wear and decay of already existing rocks and deposited elsewhere, usually by water. Over time, heat and pressure altered the character of these rocks and turned them into metamorphic rocks. In the most western zones of Colorado, these rocks are buried under thousands of feet of later deposits, but in the mountainous zone they have been forced up by the tremendous earth movements that created the Rocky Mountains. 
During the Cretaceous or Chalk period, with estimated dates extending from sixty to one hundred twenty-five million years ago, the area's most important geological changes took place. The events of this period formed much of the magnificent scenery that has made the region famous, many of the great natural resources that have provided its wealth, and the expansive natural barriers that slowed southwest Colorado's development. During the Cretaceous period, southwestern Colorado was covered with dense fern forests in which grew primitive uni-sexual flowers; some trees, ferns and club mosses attained heights of sixty to one hundred feet.  As this vegetation fell and decayed, thick layers of peat formed, and when covered and pressurized by layers of mud and sand, they were transformed and hardened over time into the rich coal beds now found in the three areas of southwestern Colorado known as the Uintah, the La Plata, and the Tongue Mesa Coal Beds.  Late in the Cretaceous period, a great mountain-making epoch began. It was a time of tremendous upheavals and great disturbances of the earth's crust. Rocks stretched and folded as arching occurred and elevation increased. There was much volcanic action and streams of molten rock poured from the earth or were deposited in the veins and faults of surface rocks. During these volcanic eruptions and crustal warpings of the Tertiary period of the Cenozoic Era, the most recent sixty million years of geological history, the Rocky Mountains and the Colorado Plateau were formed.  This period also witnessed the formation of the precious mineral ore deposits that have brought wealth and industry to southwestern Colorado. During the final geologic era, the Pleistocene or Glacial period, primitive hunters, known for their finely chipped Folsom points, entered the region that now comprises southwest Colorado more than ten thousand years ago.
The significant events of geologic history have made Colorado the "Mountain State" of the United States. As the Rocky Mountains set off the Great Plains to the east, they also delineate a definite province in the western portion of the state.  The geographic character of southwestern Colorado is diverse, yet can be easily defined by two distinct land forms.
The mountainous zone, a complex of ranges where peaks reach elevations of between 10,000 and 14,000 feet, is the eastern boundary of the area along the Continental Divide. The large montane area of southwestern Colorado has no definite pattern or form. The character is of irregularly spaced and isolated groups. In the east central section of the district the San Juan Mountains, one of the most diverse ranges in Colorado, rise to form a rugged and spectacular system that has been the center of scenic and mining attraction for the last century of the region's history. To the north of the San Juan Mountains are the Elk Mountains and the West Elk Mountains. Although somewhat less rugged than the San Juans, the Elks and West Elks are similar to the San Juans in that the three systems were formed by the volcanic action of the Cenozoic Era. Smaller ranges such as the Uncompahgre, the San Miguel, La Plata, and La Sal are found in the west and central section of the region.
To the west of the mountainous zone lies a plateau zone where high mesas and tables are dissected by rivers which have carved deep, narrow canyons with steep walls. Only in the canyon bottoms do elevations reach much less than 5,000 feet, and some of the plateaus are as much as 11,000 feet above sea level.  The Colorado Plateau province is dominated by canyons, cliffs, plateaus and broad valleys. Because of the elevation in the area, the major Colorado River tributaries such as the Gunnison River and the Uncompahgre River, draining much of the southwest Colorado region, are cut deeply into the strata. This entrenchment has created hundreds of isolated canyons and mesas.  The major formations of this type are seen in the Uncompahgre Plateau and the Black Canyon of the Gunnison River. The Uncompahgre Plateau, an abrupt uplift of sedimentary rocks which lies at elevations of 8,000 to 10,000 feet, stretches in a northwest to southeast direction from the Colorado-Utah border into the San Juan Mountains.  The Black Canyon of the Gunnison River, with a length is fifty-five miles, begins near Sapinero and extends almost to the town site of Austin. The canyon measures from 1,725 to 2,240 feet in depth and 1,000 to 3,000 feet in width. The Black Canyon National Monument, created in 1933 by President Herbert Hoover, measures ten miles long. 
The most extensive drainage in the entire southwestern part of Colorado is that of the combined Gunnison-Uncompahgre River Valleys. The total course of the Gunnison River is about 200 miles with an average rate of fall thirty feet per mile. Altogether it drains an area of approximately 2600 square miles.  The Gunnison River drainage has numerous tributary systems: Tomichi Creek, Ohio Creek, Willow Creek and Cochetopa Creek and the Taylor River on the east; the Lake Fork of the Gunnison River; and the North Fork of the Gunnison River. The Uncompahgre River rises between the head of the Lake Fork of the Gunnison River and Henson Creek to the east, near the head of the San Miguel River to the west and just opposite the Animas River on the south.
The river system, in combination with the Animas River, the San Miguel River, the Dolores River, and the San Juan River, although unnavigable, has determined the areas of irrigated agriculture, ranching, transportation, and the location of many cities and towns in southwestern Colorado. The San Miguel River, during most of its course flows through a deep canyon, and passes through or near gold and silver mining camps as well as new towns created by uranium discoveries. Among the former are such towns as Sawpit and Placerville, and among the latter are towns such as Vanadium and Uravan. The Dolores River rises in the San Juan Mountains on the border of Dolores and San Juan Counties near Lizard Head Pass. The main branch, the North Fork, begins in the San Miguel Mountains, and is joined in northern Montezuma County by another branch, the South Fork (or Bear Creek). The major valley of the San Miguel, the Paradox Valley is located in western Montrose County. In the region of such streams as Yellowjacket, Hovenweep, and Dove Creek, oil discoveries, uranium finds, and archaeological locations of ancient Indian civilizations have caused the Dolores River Valley to become one of the fastest developing centers in the region.  The Animas River has played a large part in the history of southwestern Colorado. Between Mineral Point and Silverton, it flows past Animas Forks, Eureka, and Howardsville, three major historic mining towns of the San Juan district. The chief tributary of the Animas from the north is Cement Creek which starts in the Red Mountain area just across the crest from the source of the northward flowing Uncompahgre River. Southward from Silverton, the Animas River flows through Durango, across the Southern Ute Indian Reservation, and into New Mexico.
Southwestern Colorado is an area of geographical complexity, and as a result climatic conditions vary widely within short distances. The mountains of the Continental Divide provide an effective barrier to moisture-laden air that reaches into the plains from the Gulf of Mexico. Winter temperatures are extremely cold at higher elevations and vary from cold to seasonably mild in the extreme southern and western sections of the region. Summer temperatures, except for the higher elevations, are warm. Precipitation falls from air of Pacific origin and occurs most frequently in the winter half of the year. There is a winter maximum of precipitation over the higher elevations in the region, with summer maximums at the lower elevations. From fall to spring, considerable snowfall accompanies low pressure storms.  Climatic conditions and geographical location determine the length of the growing season, the quality, type, and abundance and/or lack of ground cover. The Gunnison River Valley, with many sources of water from high elevation drainage and annual precipitation, has rich bottomland vegetation. In the Mancos River Valley, where these conditions do not prevail to such an extent, only sparse vegetation occurs. Moisture in the mountainous areas encourages a heavy growth of aspens, pine, fir and spruce trees, and wildlife abounds in these favorable conditions.
*These figures were obtained from the 1918 edition of the Colorado Yearbook, pp. 15-16.
Taken in the large, the topography, climate, resources, and general physical conditions of southwestern Colorado have made possible the development in the region. Yet the nature of its geography and a certain physical isolation that existed as a result, have controlled not only the extent of physical exploitation of the land, but cultural contacts as well. This isolation has had the effect not so much of removing the region from inter-cultural contacts in the early period of its development as of selectively focusing the nature and scope of those contacts. Geography then, is a key to much of the history of southwestern Colorado. Miners, ranchers, and railroad builders have been, like the Indians who preceded them, controlled by and pre-occupied with their geographic environment.
The earliest periods of use and occupation in southwestern Colorado can be characterized as ones of adaptation and transition to geographic and climatic conditions. The several prehistoric cultures, perceived and reacted to their environment in a variety of ways.
9. United States Department of the Interior, Bureau of Land Management, Proposed Development of Coal; West Central Colorado Final Environmental Statement, Vol. I (Denver: Bureau of Land Management, Colorado State Office, 1979), p. 79.
Last Updated: 20-Nov-2008