A Brief History of Humans
in the Southwestern United States 

To supplement our coverage of some of specific impacts of human development on the Southwest, we thought it would be helpful to provide a brief review of some important historical events.  First is a timeline giving some of the most important events.

1300 - Anasazi (ancestors of the Pueblo tribe) civilization abandoned
1400 - Hohokam (ancestors of the Papago and Pima tribes) civilization abandoned
1400 - Ute and Paiute civilizations thrive and the the Navajo, Pueblo, Pima, Papago, Apaches, and Comanches arrive in the southwestern United States
1536 - Spanish explorers begin to launch several expeditions from Mexico
1540-1542 - Francisco Vasquez de Coronado leads an expedition
1802-1806 - Lewis and Clark expedition sent by Thomas Jefferson
1820's and 30's - The height of the fur industry in the West
1849 - The beginning of the California Gold Rush
1851 - The Mormons arrive in the Salt Lake Valley, Utah                                      Major John Wesley Powell
1869 - The Powell Geographic Expedition sets out to explore the Colorado
1862 - The Desert Lands Act becomes law
1890's - The rise of the federal irrigation movement
1902 - The Bureau of Reclamation is created
1930's - The Reclamation program activity goes into high gear
1935  - Boulder Canyon Dam - Hoover Dam - is completed
1985 - The Central Arizona Project (CAP) delivers water to the interior of Arizona

Richard White in his book A History of the American West, states that "the West had ceased to be wilderness long before the first Whites ever arrived."  The vegetation and land of the Southwest reflected American Indian use, long before either the Spanish or the Americans began to colonize the Southwest.  The origins of all the western American Indian tribes and their relationships to one another are not known. However, there are thought to have been three basic American Indian culture groups living in the Southwest before the Spanish arrived in the sixteenth century.  First there were the nomadic hunters and gatherers, second the Hohokam people of present Arizona and Sonora, and third the Puebloan people of the Colorado Plateau (Baker et al 1973).

The Hohokam and Puebloan people were village dwellers, and agriculturalists.  Some of the irrigation ditches of the Hohokam people, were 25 feet wide and 15 feet deep, and their total mileage equaled about 150 miles (Hollon 1966). The following photograph shows a Hohokam irrigation canal in 
central Arizona dated to about 800 A.D. (Baker et al. 1973).  The Pima word Hohokam means "those that have vanished" and the Hohokam did disappear around 1400.  All major Indian cultures showed signs of stress during the 12th and 14th centuries, and Robert H. Lister, the chief of the New Mexico Archaeological Center in Albuquerque says overpopulation was the problem.  Lister cites evidence of hills stripped of timber, increased erosion, and deepening arroyos in Pueblo Bonito a site of the Anasazi civilization that was abandoned around 1300 (Findley 1878).

Charles Bowden, in Killing the Hidden Waters, describes the Papago tribe as "a society perfectly adapted to aridity and absolutely independent of groundwater."  The Puebloan people built agricultural terraces at the mouths of small arroyos (deep gullies cut by an intermittent stream), with a series of stone terraces that would catch all available water.  They also built stone reservoirs for water catchment and long-term storage (Baker et al 1973).

In the sixteenth century, Spanish explorers and settlers came to the Southwest looking for gold.  In the process they introduced cattle, horses and sheep, new irrigation techniques, ranching and laws governing the land. One of the most extensive Spanish exploration expeditions was led by Francisco Vasquez de Coronado beginning in 1540.  This expedition headed up the Rio Grande valley as far as the plains of Kansas and laid the foundation for future Spanish missionary work.  It also provided the first written description of the Southwest.  In his book, Cadillac Desert, Mark Reisner states that other lasting impacts of the Spanish settlement were the huge California land grants established by the King of Spain, some of which still persist as large ranches to this day.

It is the settlers from the United States which have had by far the largest impact on the southwestern United States.  The growing population has caused huge environmental changes in the Southwest.  The drastic increase in the amount of land devoted to irrigated agriculture, and cattle ranching has resulted in the degradation of riparian habitat, the introduction and establishment of invasive species, and desertification.  Americans began to enter the Southwest in the early 1800's, and settlers really began to pour in after the end of the Mexican War in 1848, when the United States acquired most of the land in the Southwest.  The discovery of precious metals was also a major cause of immigration to the Southwest, the Santa Fe Trail was the route that many settlers took to get to New Mexico.  The mining frontier "leapfrogged" from Montana and Idaho to Utah and Wyoming and all the way down to southern Arizona (Hollon 1966).

Probably the most successful of the early American settlers were the Mormons who arrived in the Salt Lake Valley of Utah in July 1847.  They immediately began to build massive irrigation systems, and have remained a powerful presence in the state of Utah to this day.

Environmental changes in the Southwest occurred when settlers plowed under native plants, and introduced new species at an increasing rate over the course of the 19th century (White 1991).  The land was also greatly impacted by the growing cattle industry. Overgrazing resulted in the invasion of non-native grasses to the Great Basin grassland.

John Wellesley Powell is a very important figure in the history of the Southwestern United States, he had a huge impact on American settlement because he had a desire to open up the West to rapid economic settlement and development.  In May 1869 the Powell Geographic Expedition set out on the Green River, headed down the Colorado and was the first expedition to float the length of the Colorado.  Powell knew that water was the key to the development of the West.  He believed that water should be federally developed through dams, canals and ditches and then have its use controlled at the local level in democratic districts (White 1991).  By the late 1870's the 100th meridian had been crossed, meaning settlements were quickly spreading westward.  Settlement was encouraged by false propaganda such as the saying "rain follows the plow."  This propaganda was created by Ferdinand Hayden another explorer like Powell who also wanted to open the west up to rapid development.  The faulty logic behind this was that the rains appeared to be coinciding with the westward advancement, so the two must be somehow related.

In the Southwestern United States water is usually the most limiting factor to the development of human settlements.  Therefore, the damming and diverting of water has been major projects in the southwest during this century.  In 1902, an act called the Newlands Act was passed, which established the U.S. Reclamation Service, and the Federal Government began large scale construction of irrigation projects.  The city of Los Angeles grew from 50,000 in 1890 to 200,000 in 1904, and this growing city required more water.  Unfortunately the water they needed was in the Owens River which was 250 miles away.  It took six years to complete, but due to the work of William Mulholland and Fred Eaton a system of aqueducts and tunnels were built diverting the Owens River to Los Angeles (Ward 1996).

However, it was not until the 1930's that the Bureau of Reclamation became successful in its goal to irrigate many acres of the West.  The completion of Boulder Dam on the Colorado River in 1935 was a major accomplishment for the Bureau of Reclamation.  The success of this project marked a shift from small scale local development projects to huge federal projects affecting whole regions of the country.  By the 1930's urban centers in the southwest had already begun to grow rapidly, for example Los Angeles continued to grow from 200,000 in 1904 to 1.2 million by 1930.  The following diagram illustrates the states with the fastest growing populations (White 1993).  The states which are shaded gained more than 1 million new residents between 1940-1980, and the dots represent cities whose populations grew by at least 180,000.  The city of Las Vegas is growing by 1,000 people each week (Cohen 1997).

One of the last and most costly of the huge reclamation projects was finished in 1985 when the Central Arizona Project (CAP) was completed.  The CAP consists of a 333 mile aqueduct, with pumps that lift the water 2,900 feet above its point of diversion in the Colorado River and deliver it to the interior of Arizona (Reisner 1993).

By the 1970's there were 1,251 major reservoirs in California, and all but one significant river in this state had been dammed at least once.  At this point in time the Colorado has been dammed and diverted so drastically that it's flow no longer makes it all the way to the ocean.  The Rio Grande has reached a similar fate.  The Rio Grande is only a dry river bed for about 290 miles, until tributaries in Mexico such as the Rio Conchos enter in and replenish its flow (Findley 1978).

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