Old Spanish Trail National Historic Trail, 1829-1848In 2002, Congress designated the Old Spanish Trail (OST) as America's 15th National Historic Trail, to acknowledge the significant role that this long-distance trail network played in the exploration and settlement of the interior Mountain West, southern Nevada, and southern California.

The OST is jointly administered by BLM and the National Park Service along its 2,700 mile length, in partnership with other federal, state, tribal, and local government agencies, as well as private land owners, that administer or own lands along the trail.

Between 1829 and 1848, commercial traders, explorers, horse thieves, and settlers traveled this difficult pack trail between the Spanish colonies in New Mexico and southern California. Each spring, trade caravans left Santa Fe with dozens of pack mules loaded with woolen blankets woven in New Mexico and made the lengthy trek to southern California's coastal settlements. This long distance pack trail network came to be known as the "Old Spanish Trail".

The primary travel route, labeled the Northern Route of the OST, passed through northeastern New Mexico, western Colorado, along nearly the entire length of east-central Utah, across the hot, arid Mojave Desert of southern Utah and Nevada, and finally through the mountain passes of southeastern California.

Bartering and selling their blankets and serapes in California for horses and mules and exotic goods, like silk from China, the traders drove large herds back to New Mexico along this route. Over time, multiple, parallel, and intertwined routes developed, many following trails that had long ago been pioneered by American Indians.

In 1848, New Mexico began charging a duty on goods being packed to California, reducing the profitability of the commercial trade caravans. Wagon traffic increased and use of the OST as pack trail declined dramatically after this date.