Juan Rivera (explorer)

Juan Maria Antonio Rivera (also spelled Ribera) was an 18th-century Spanish explorer who explored southwestern North America, including parts of Southern Rocky Mountains. In 1765, at the request of Governor Tomás Vélez Cachupin of New Mexico, he led an expedition from Santa Fe northward through present-day Utah and Colorado, partly in search of silver but also to help thwart the expansion of European powers in the region. His expedition passed through regions inhabited by the Ute and Southern Paiute tribes. His expedition cross the Los Animas River near present day Durango, Colorado (a tributary of the Colorado River), which he may have named. The ore samples he brought back to Santa Fe were among the first recorded discoveries of gold in present-day Colorado, although they created no particular interest at the time.
References.
Jacobs, G. C. 1992. "The Phantom Pathfinder" Utah Historical Quarterly 60(3): 201 - 223.