The American bison (Bison bison) is a North American species of bison, also commonly known as the American buffalo. These bison once roamed the grasslands of North America in massive herds; their range roughly formed a triangle between the Great Bear Lake in Canada's far northwest, south to the Mexican states of Durango and Nuevo León, and east along the western boundary of the Appalachian Mountains. Today these bison are much fewer in number, and travel only in small herds.