A fluffy white tail arches dramatically over a rust-red body as this remarkable Kaibab squirrel — found nowhere else on Earth — pauses on a sun-warmed pine branch above the North Rim of the Grand Canyon. The Kaibab squirrel (Sciurus aberti kaibabensis) evolved in total isolation atop the Kaibab Plateau, making it a textbook example of allopatric speciation; Union Pacific Railroad leveraged that scientific celebrity to lure tourists westward, distributing promotional linen-era pictorial cards like this one through its famed "Overland Route" tour packages. The vivid hand-toned color — deep sienna fur contrasted against a cloud-blue Arizona sky — is typical of the high-quality linen stock Union Pacific commissioned in the 1930s–40s, and the card's catalogue number 122325 helps date it firmly within that promotional campaign era.