The cutthroat trout is the most diverse trout species in North America. The historical distribution of cutthroats covers the broadest range of any stream-dwelling trout in the Western Hemisphere. The rugged topography of their range has lead to isolation, which in turn has given rise to fourteen recognized subspecies. Four of these species evolved in Colorado: the Colorado River cutthroat trout west of the Continental Divide, the Greenback cutthroat trout in the South Platte River drainage, the yellowfin cutthroat trout (now extinct) in the Arkansas River drainage, and the Rio Grande cutthroat trout in the Rio Grande River drainage in the San Luis Valley and northern New Mexico. The Rio Grande cutthroat was the first New World trout encountered by Europeans in 1541, by Spanish explorer Francisco de Coronado.
