Different species and lineages of cutthroat trout are found across the western states. In Colorado, there are three species of cutthroat trout in different regions of the state. Colorado River cutthroat trout live in drainages west of the continental divide, greenback cutthroat trout are in the South Platte and Arkansas River drainages, and the Rio Grande cutthroat trout are found in streams draining into the San Luis Valley, according to Parks and Wildlife. Efforts to restore the species have been ongoing since the early 1970s, when greenback cutthroat trout were listed as endangered. This species currently has a lesser-threatened classification.