The McKay Formation in Oregon is a fossil-bearing geologic unit that preserves a rich record of late Neogene life in what is now northeastern Oregon. Dated from the Tortonian through Zanclean stages and associated with the Hemphillian North American land-mammal age, it has yielded a diverse assemblage including rodents, pikas, moles, horses, camels, peccaries, the rhinoceros Teleoceras hicksi, and carnivores such as Epicyon saevus, Eucyon davisi, Lynx longignathus, and Nimravides catocopis. Bird fossils are also known from the formation. Studied since at least J. A. Shotwell’s 1956 work, it remains an important source for understanding Oregon’s ancient fauna.