Black Sand Basin is an isolated group of the Upper Geyser Basin located along the Firehole River about one mile from Old Faithful. The name derived from the black fragments of obsidian sand that covers the basin of small geysers and colorful hot springs.
Bison are the largest mammals living in the park and Yellowstone is the only place in the lower 48 where the population of wild bison has persisted since pre-historic times. They are truly majestic animals weighing up to 2000 pounds and standing 6 feet at the shoulders. In the summer you can find them in the grassy areas and in the winter they stay near the thermal areas of the geyser basins for warmth. | 
