The Yellowstone National Park Bison herd is known as the oldest and largest public bison herd in the United States. It is believed they have lived there continuously in the geothermal activity hot spot since prehistoric times along side other large mammals like the elk and moose.
Actually more dangerous than their co-inhabitants bears, the Bison should be treated with the utmost respect remembering they are wild and unpredictable. A full grown male can weigh over 900kg and measure over 3 1/2 meters in length. That's one animal you don't want to get into an altercation with.