By the late 15th century, elk were widespread in North America and could be found throughout most of the continent. Eastern elk inhabited the vast forests of the Eastern Woodlands region as far west as the Mississippi River. As people continued to settle in the region over the next few centuries, elk populations decreased due to over-hunting and the loss of their dense woodland habitat. Naturalist John James Audubon reportedly mentioned that by 1851, a few elk could still be found in the Allegheny Mountains, but that they were virtually gone from the remainder of their range. By the end of the 19th century, the eastern elk was completely extinct. What little is known about this race of elk has been gleaned from remains and historical references. Mitochondrial DNA studies in 2004 indicate that Cervus canadensis are a species distinct from European red deer.