The Spanish Trail consisted of a 1,120-mile northward-looping course traversing six states--New Mexico, Colorado, Utah, Arizona, Nevada, and California. Hostile Indian tribes--Apaches, Navajos, and Mojaves--prevented the opening of a direct route between Santa Fe and Los Angeles. To circumvent the great canyons of the Colorado River system, the trail was pushed northward to the open country at Green River, Utah.
The word "Spanish" is something of a misnomer since the trail was in use only during the time when the region traversed was part of Mexico. The term comes down to us in the writings of American explorers who, as they traveled along sections of the trail, concluded that it had been opened by Spain. Thus it appears in their diaries and maps as the "Spanish Trail." John C. Frémont was one of those who used the name. After 1848, when sovereignty of the region passed to the United States, American travelers in some numbers described the "Old" Spanish Trail, and their writings provide clues for anyone seeking its location.
The trail was simply that--a trail; it was not used by wheeled vehicles until 1848 when the Mormons developed the western section for wagon travel between Salt Lake City and southern California. It was the first extensively used route to cross the region now within the boundaries of Utah. The Utah sector, the longest of any within the trail states, was 460 miles. Recently completed field research has revealed the actual location of the trail throughout its course from Santa Fe to Los Angeles.