In 1973, the U.S. Fish and Wildlife Service (FWS) listed the northern Rocky Mountain wolf (Canis lupus) as an endangered species and designated Greater Yellowstone Ecosystem (GYE) as one of three recovery areas. From 1995 to 1997, 41 wild wolves from Canada and northwest Montana were released in Yellowstone.
https://www.nps.gov/yell/learn/nature/wolves.htm

