We found 13 specimens (11 museum skins, 2 skeletons) of White-tailed Ptarmigan (Lagopus leucura) collected in Wyoming. All were collected in the 1911–1967 period: 12 from the Snowy Range (Albany County) and one from near Encampment (Carbon County). The last verifiable observations of White-tailed Ptarmigan in the Snowy Range were 2 separate reports in 1974, both of 4 individuals in the same location. A more recent report of 2 birds north of the Snowy Range on 15 October 2005 has also been verified. None of the verifiable observations or collection events was of more than 6 individuals. Most of the published observation records from areas other than in the Snowy Range were of single individuals and were likely Dusky Grouse (Dendragapus obscurus). Field investigations in the Beartooth Plateau, Bighorn Mountains, and Wind River Range outside of the Snowy Range revealed no ptarmigan or their sign. However, all unoccupied areas examined could potentially support White-tailed Ptarmigan populations, with the Wind River Range being most suitable, followed by the Bighorn Mountains and Beartooth Plateau. The lack of White-tailed Ptarmigan in alpine areas in Wyoming outside of the Snowy Range is most likely related to geologic events in the late Pleistocene period and not in the Holocene.