The wolf is a major predator that had been missing from the Greater Yellowstone Ecosystem for decades until its restoration in 1995.
- Late 1800s– early 1900s: predators, including wolves, are routinely killed in Yellowstone.
- 1926: The last wolf pack in Yellowstone is killed, although reports of single wolves continue.
- 1974: The gray wolf is listed as endangered; recovery is mandated under the Endangered Species Act.
- 1975: The long process to restore wolves in Yellowstone begins.
- 1991: Congress appropriates money for an EIS for wolf recovery.
- 1994: EIS completed for wolf reintroduction in Yellowstone and central Idaho. More than 160,000 public comments received—the largest number of public comments on any federal proposal at that time.
- 1995 and 1996: 31 gray wolves from western Canada relocated to Yellowstone.
- 1997: 10 wolves from northwestern Montana relocated to Yellowstone National Park; US District Court judge orders the removal of the reintroduced wolves in Yellowstone, but stays his order, pending appeal. (Decision reversed in 2000.)
- 1995–2003: Wolves prey on livestock outside Yellowstone much less than expected: 256 sheep, 41 cattle
- 2005: Wolf management transfers from the federal government to the states of Idaho and Montana.
- 2008: Wolf populations in Montana, Idaho, and Wyoming removed from the endangered species list, then returned to the list.
- 2009: The US Fish and Wildlife Service again delisted wolf populations in Montana and Idaho, but not in Wyoming. A legal challenge resulted in the Northern Rocky Mountain wolf population being returned to the federal endangered species list.
- 2011: Wolf populations were again delisted in Montana and Idaho by action of Congress within the previous year, and the US Fish and Wildlife Service proposed delisting wolves in Wyoming.
- 2012: Based on a Congressional directive, wolves were delisted in Wyoming and the Northern Rocky Mountain Distinct Population is no longer listed.
Wolves are now delisted throughout the northern US Rocky Mountains, including Wyoming. The US Fish and Wildlife Service will monitor the delisted wolf populations for a minimum of five years to ensure that they continue to sustain their recovery.