Spanish influence moved northward from Mexico and resulted in the founding of Santa Fe in 1609, and the establishment of a number of military installations along the Rio Grande.
In the 18th century, Spain dispatched Father Junípero Serra into Alta California for the purposes of Christianizing the Native Americans and supporting the Spanish claim to the area against Russian expansion. Serra established the initial parts of a string of missions along El Camino Real ("The King's Highway"), stretching 700 miles from San Diego to Sonoma.
In 1821, Mexico won her independence from Spain and ended the restrictive trade policies of the colonial era. The first American to tap this new market was William Becknell, who carted goods from Missouri to Santa Fe. His mixture of manufactured goods was traded for Mexican gold and furs. This lucrative venture was repeated for a number of years.
Only very slowly did Americans come to realize that the Great Plains area held economic benefits. The region was written off by the initial visitors and labeled it the Great American Desert on maps. The immense grasslands would not support forests or the production of cotton and were largely ignored until traders and trappers began to discover the region’s potential.