Among the iconic mammals of the North American West is the mule deer (Odocoileus hemionus). This species and a western subspecies of the white-tailed deer (Odocoileus virginianus macrourus) were two of seven mammals originally named and described as new species in 1817 by Constantine S. Rafinesque. Rafinesque never saw the animals that he named. Instead, he followed the then-acceptable practice of basing his new species on animals characterized in another published work, in this case the putative journal of Charles Le Raye, a French Canadian fur trader who was said to have traversed the upper Missouri River region before the Lewis and Clark Expedition and whose journal described some of the wildlife in detail. Unlike the mule deer, whose existence has been established by generations of biologists, wildlife management professionals, and sportsmen, Le Raye and his journal have since been proven to be fraudulent. Because Rafinesque’s names were published in accordance with the taxonomic conventions of his time, they remain available, but, based on the questionable source of his descriptions, the identities and type localities of the species must be viewed as unreliable. Fortunately, much of the Le Raye journal was derived from other, verifiable contemporary sources. In particular, the descriptions of the two deer were based on the published journal of Patrick Gass, a member of the Lewis and Clark Expedition. Using the Gass journal as the original source of Rafinesque’s descriptions, the type localities for the two deer can be reliably placed in Lyman County, South Dakota.