The Black Hills [1] occupy an area of approximately 65 by 125 miles; while the area is small, the diversity is great. Located in the middle of the country, surrounded by grasslands and plains, the Black Hills form the ecological junction of many regions. Here can be found wildlife and plant species typical of the Rocky Mountains, the Great Plains, northern forests, and eastern forests.
Links:
[1] http://www.moon.com/destinations/mt-rushmore-the-black-hills/discover-mount-rushmore-the-black-hills