Established in 1872, Yellowstone is the first US National Park. Famous for its wildlife and geothermal activity, the park covers almost 3,500 square miles (9,000 square kilometers) stretching over parts of Wyoming, Montana, and Idaho. The park boasts one of the largest high-altitude lakes in North America (Yellowstone Lake), the longest undammed river in the contiguous United States (Yellowstone River), and even its own “Grand Canyon”.