Greater Yellowstone Ecosystem
The Yellowstone National Park boundaries were drawn in 1872 to include all the geothermal basins in the area. By the 1970s, the grizzly bear's (Ursus arctos) range in and near the park became the unofficial minimum boundary of a Greater Yellowstone ecosystem. This had at least . Since then, definitions of the greater ecosystem's size have steadily grown larger. A 1994 study listed the size as , while a 1994 speech by a Greater Yellowstone Coalition leader enlarged that to .