From Trail Gazette:
Before European settlement, gray wolves thrived across the Lower 48 states and were at one time considered the most widely distributed land mammal in the world.
But by the 1960s, gray wolves were essentially eradicated from their historical range. Only a small population remained in the deep woods of northern Michigan and Minnesota at that time. Colorado’s wolf population was believed to be eliminated by about 1940, according to Colorado Parks and Wildlife (CPW).