The Yellowstone Park bison herd in Yellowstone National Park is probably the oldest and largest public bison herd in the United States. Yellowstone is known for its geothermal activity and large mammals, especially elk, wolves, American bison, bears, pronghorns, moose and bighorn sheep. The Yellowstone Park bison herd was estimated in 2015 to be 4,900 bison The bison in the Yellowstone Park bison herd are American bison of the Plains bison subspecies. Yellowstone National Park may be the only location in the United States where free-ranging bison were never extirpated, since they continued to exist in the wild and were not re-introduced, as has been done in most other bison herd areas. Other large free-ranging, publicly controlled herds of bison in the United States include the Wind Cave b