President Ulysses S. Grant signed legislation making Yellowstone this country’s first national park on this date in 1872. Yellowstone covers nearly 3,500 square miles, and is home to one of the world’s 30 active super volcanoes. The volcano lies underneath Yellowstone Lake, and it’s responsible for some of the more dramatic of the park’s features, including hot springs, mud pots, and the famous Old Faithful and Steamboat Geysers.