Yellowstone National Park needs no introduction. In 2010, more than 3.6 million people thronged the park, and if recent trends are any indication, that number will only continue to climb [source: National Park Service]. Spanning nearly 3,500 square miles (9,065 square kilometers) of the northwest corner of Wyoming, Yellowstone has become a symbol for the importance of preservation efforts. Although Yellowstone is well-known for its geysers and other geothermal features, it's also home to an incredibly diverse spectrum of plants and animals. For instance, the park hosts 67 different species of mammals, a group that includes the well-known grizzly bear and bison alongside lesser known animals like the wolverine and the lynx [source: National Park Service]. A remarkable variety of birds – more than 300 species in all -- call the park home as well, including threatened and endangered species like the whooping crane [source: National Park Service].
Visitors to Yellowstone have no shortage of things to do. In addition to activities like biking, boating and fishing, guests can also go horseback riding, take guided tours through the park and go camping. Granted, visitors need to exercise some precaution as they explore Yellowstone, particularly if they come across animals like bear and bison, but the sprawling, spectacular park offers an unprecedented glimpse into one of the most varied ecosystems in the United States.
While Yellowstone has an impressive amount of wildlife, you'll have to head north if you're interested in animals of the prehistoric variety.