The ancient Indian trail known as El Camino del Diablo, the "Devil's Highway", stretches across the forbidding mountains and deserts of southwestern Arizona. Traditionally, the Camino del Diablo began in the east at Caborca, Mexico. The trail meandered northwestward to Sonoyta, then westward to its terminus at Yuma, Arizona. Some of the most rugged and dangerous country in North America is encompassed by the Camino del Diablo. This part of the southwest lies in the Sonoran Desert biome and is home to a number of America's most venomous creatures. These include the small but dangerous straw-colored scorpion known as Centruroides sculpturatus, the lethal Black Widow spider, the poisonous lizard known as the Gila Monster (one of only two species of venomous lizard known in the world), the Sonoran Coral Snake, and some 16 species of rattlesnake (including the deadly Mohave rattlesnake which has a venom that is both neurotoxic and hematoxic).
The "Devil's Highway" was an old and venerable pathway centuries before the white men came. Arrowheads and pottery fragments can still be found in many locations along the trail. Of course, the first white men to penetrate the region were Spaniards from Mexico. In 1540, Melchior Diaz became the first Spanish explorer to traverse the trail. Nearly 160 years later, Father Eusebio Kino and the renowned Indian fighter Lieutenant Juan Manje traveled the "Devil's Highway" on their way to the Colorado River Indian villages. In 1779, Father Garces made the journey and in 1781, a group of Spanish families led by Santiago de Islas followed the trail to Yuma. These were hard years for the Spanish in this part of the American Southwest. Indian attacks beginning in 1781 and continuing through the 1790's effectively cleared the area of white men. Finally, by the beginning of the 19th century, Spanish migration into the area picked up again but traffic along the trail was never heavy. It required an extraordinary event in central California in 1848 to resurrect the Camino del Diablo of southwestern Arizona.
In 1848, the incredible gold fields of California were discovered. By 1849, scores of prospectors were streaming to the Mother Lode country. The "Devil's Highway" served as a major route for Mexican prospectors on their way to California. It was during this period that the "Devil's Highway" earned its name - nearly 2000 people died of thirst along the trail.
In 1850, a party of Mexican prospectors entered the forbidding wilderness of southwest Arizona, using the Camino del Diablo as their trail. This particular group of prospectors eventually made their way to the rugged Agua Dulce Mountains where they made camp. (Some accounts have them camping near Tinajas Altas, located west of the Cabeza Prieta Mountains). In any case, the following morning the Mexicans found some of their stock missing. The prospectors fanned out in search of them. One of the Mexicans made his way to a small mountain located east of the prominent landmark known as Cabeza Prieta ("Black Head") Mountain. While climbing the small peak the Mexican stumbled onto a rich vein of gold-bearing quartz! The vein was nearly two feet wide and consisted of red hematitic quartz laced with coarse gold and rare wire gold.
The Mexican collected samples of the amazingly rich ore and eventually rejoined his friends. The party of Mexicans continued on to Sonoyta but when they attempted to return to the mine, they were ambushed and killed by Papago Indians. (At least one account of the story has one of the Mexicans surviving the attack.)
This part of southwest Arizona contains a few other mines besides the Ajo prospects. Some of these mines were quite rich - one of the most famous of these was the Fortuna Mine, located on the western flank of the Gila Mountains, near the western terminus of the Camino del Diablo. In fact, the mine portal lies within a few hundred feet of the old trail itself! The Fortuna Mine produced some 3 million dollars in gold around the turn of the century. This is somewhat amazing since thousands of 49er's and later emigrants passed through the area and apparently none of them bothered to search the Gila Mountains for gold. Consequently, they all missed the fabulous Fortuna vein! The Copper Mountains and the Cabeza Prietas also contain mines, but in general, this part of southwest Arizona is weakly mineralized. The mining history of the area is therefore quite sparse.