Bison are an ancient species, with fossils tracing their ancestors to over 400,000 years ago in Asia. Scientists believe that at some point, bison began crossing the land bridge that once connected to North America. They spread far and wide, all the way to Mexico and New England. But the largest concentration of bison was here on the Great Plains, with an estimated 60 million of roaming the Midwest. The abundance made bison an excellent source of food and materials for Native Americans. This way of life could have continued, had it not been for the white settlers who hunted the species to near extinction.