San Pedro River: A Linear Oasis

The San Pedro River marks the western edge of the Chihuahuan Desert. It is a small, struggling, vital, and enormously diverse river, thronged with ghosts. The last undammed river in a region where an estimated 90 percent of the precious riparian areas have been destroyed or degraded, the San Pedro nurtures great, leafy meanders of cottonwoods and willows. It is not endangered like so many already ruined desert rivers by groundwater pumping and drought, and it has sustained human beings for millennia. It remains one of the most diverse and vital places in this surprisingly rich desert country.

The San Pedro forms a linear oasis in the midst of an otherwise harsh desert, offering a respite for desert dwellers and a food-rich, ecological highway for other species that migrate from the winter-friendly tropics to the summer-bountiful sprawl of North America. That is why cottonwood and wetland habitats like the San Pedro rank as among the most biologically productive in the world and why more than 200 species of birds flutter through the multistoried canopy. It has also played a vital role in the history of the region as its water nourished ice age mammoth hunters, Spanish conquistadors, Apache raiders, pueblo builders, feuding gunfighters, desperate ranchers, bereaved fathers, arrogant mining magnates, and a host of other heroes and villains.

The human saga of the San Pedro starts for certain between 11,200 and 8,000 years ago, with the arrival of a mysterious group of big game hunters who tipped their sturdy stone spears with distinctively fashioned stone points, called Clovis points, named after where they were first discovered in Clovis, New Mexico. These Clovis culture hunters probably were descendants of people from Europe who crossed the Bering Strait between 50,000 and 15,000 years ago when the ice age expansion of the polar ice cap drew down the sea level and exposed the land bridge. The wandering hunter-gatherers fanned out across North America during the wet extravagance of the last ice age, undoubtedly following great herds of mammoths, camels, horses, bison, and tapirs. Paleontologists have identified some 37 important sites along the San Pedro where they have unearthed the bones of animals up to 7 million years old. They've also found at least two places where a combination of extinct animal bones and distinctive Clovis stone points denote an area where these big game hunters killed and butchered their prey. These finds make the San Pedro one of the best places in the country for studying the first appearance of human beings in North America and perhaps their impact on the awesome herds of gigantic animals like mammoths who became extinct in the face of human hunting and the climate change at the end of the Ice Age.

The San Pedro also harbors more than a dozen places where archaeologists have unearthed the remains of people of the Cochise culture, who occupied the area between 8,000 and 2,000 years ago. They probably discovered agriculture, but relied mostly on gathering wild plants and hunting the small game animals left after the disappearance of monsters like the mammoths and the sloths. They hunted with spears and chipped stone knifes, made simple baskets, dry farmed almost wild corn crops, built simple brush shelters, and left behind a scattering of grinding stones and other tools. They also left behind scattered clues to a momentous discovery, the development of agriculture.

They were succeeded by outriders of the Mogollon, Hohokam, and Salado cultures between a.d. 1 and a.d. 1450. These people built pit houses and pueblos, dug irrigation ditches, planted corn, beans, and squash, fired pottery of beautiful shapes and designs, and incorporated the San Pedro River valley into a linked network of cultures that reached from California into New Mexico and down to the thriving empires of South America. This complex web of civilization collapsed in the 1400s for reasons that remain mysterious, but the San Pedro remained one of the few areas still occupied after the regional collapse.

The first Spanish explorers found the rich river valley occupied by the Sobaipuri Indians, who lived in small villages, built simple shelters, farmed the river bottom and terraces, and defended themselves from sporadic raiding by the warlike Apache Indians, recently arrived wanderers. Fray Marcos de Niza marched through the valley in 1539 and found the Sobaipuri friendly and anxious for an ally against their enemies, the Apaches. Francisco de Coronado's gigantic expedition in fruitless search for the mythical Seven Cities of Gold passed through the valley in the next year, and Father Eusebio Francisco Kino visited the Sobaipuri in 1692. Kino provided the Indians with seeds and cattle, but wasn't much help in fending off the Apaches. Ironically, the arrival of the Spanish may have actually escalated the Sobaipuri's war with the Apaches. The warrior culture of the Apaches quickly adapted to the horses and weapons of the Spanish and found that the horse and livestock herds the Spanish established around their missions greatly increased the payoff for conducting raids, which could now easily range over 1,000 miles (1,609 km) with the help of stolen horses.

Warfare with the Apaches escalated sharply with the arrival of the Spanish. In 1772 the Spanish decided to take advantage of the cooperative Sobaipuri on the San Pedro to help build the northernmost fort of their New World empire. They began construction of the Presidio de Santa Cruz de Terrenate in about 1776, dispatching several hundred soldiers and colonists to build an Apache-proof fortress. The Apaches quickly saw the danger and learned the fort's weak point. Built on an easily defensible bluff overlooking the river, the fort had no water or arable ground. The Spanish quickly discovered that working their fields or getting water could prove fatal. The harassing Apaches on one occasion even stole cattle and staged a rowdy feast on the riverbank in full view of the frustrated Spaniards, who never managed to get the walls built higher than four feet. Reluctantly, the Spanish abandoned the fort in 1780, having lost 80 men in their long war of attrition with the Apaches. Acknowledging defeat, the Spanish friars moved the Sobaipuri to a more defensible settlement near Tucson. This movement of the Sobaipuri out of the valley they had farmed for nearly 300 years suggests that the intervention of the Spanish had only served to increase the reach and appetite of the warrior Apaches.

The Apaches had the almost unrestricted run of the valley for nearly a century after the Spanish abandoned their presidio. No one dared settle the San Pedro Valley for decades after the soldiers left since the Apaches moved freely along the river corridor and remained secure from any reprisals in the surrounding mountains. In an effort to encourage settlement, however, the Mexican government in 1827 and 1833 made land grants to a great ranching family. They too eventually gave up in the face of continued Apache raiding. The Apaches, the Mexicans, and the arriving stream of American settlers waged a long, bitter struggle for control of the valley. The tide finally turned against the Apache in 1846 when the United States declared war on Mexico and claimed as spoils most of New Mexico, Arizona, and California.

The U.S. Army moved into and through the valley after the Mexican-American War ended in 1848. Clashes with the Apaches who still moved through the valley with relative impunity mounted steadily, coming to a head in the 1870s and 1880s.

The ultimate fate of the San Pedro River remained in the hands of a few large-scale ranchers, including George Hearst, the father of newspaper tycoon William Randolph Hearst. The ruthless, determined George Hearst built a vast, western empire. At one time, he owned some 7 million acres in the Mexican state of Chihuahua. He also served as a U.S. senator from California in the heyday of the robber barons when fabulously wealthy industrialists easily mingled economic and political power. George Hearst left most of his San Pedro valley ranch to his son and widow.

Another large chunk of the river was owned by Colonel William Greene, a mining millionaire. He was embroiled in several violent incidents, including a murder. Greene had built a dam along the San Pedro, but it burst, causing a flood that killed Greene's daughter. Greene suspected a rival, James Burnett, of sabotaging it. He grabbed his gun, found Burnett in a saloon, and shot him dead. Greene was tried and acquitted of murder charges.

Meanwhile, uncontrolled cattle grazing in the late 1880s spawned ecological disaster when drought struck in the 1890s. Overgrazing and extermination of beavers worked dramatic ecological changes. Once the San Pedro was a long marsh created by beaver dams, fringed by an extensive mesquite forest. Thick grass covered the uplands, protecting the powdery soil. The marshes soaked up floods, and cottonwoods and willows provided a rich wildlife habitat. The overgrazing and the drought first killed millions of cattle, then resulted in the drying out of much of the river. In the process, the nature of the surrounding grassland was permanently altered, as grasses gave way to mesquite scrub and the land shifted toward desert.

A coalition of conservationist groups spearheaded by the Sierra Club and the Nature Conservancy eventually convinced the federal government to save the San Pedro through land swaps that created a 56,000-acre conservation area along 17 miles of the river's course. The federal government has since kept out cattle and brought back beaver, which has begun to restore the cottonwoods, grasses, and marshes that make the river so biologically rich. Sadly, a recent decade-long drought coupled with groundwater pumping in nearby towns have reduced flows and once again the river is threatened.