Early morning mist on the Firehole River in Wyoming's Yellowstone National Park. Yellowstone is the world's oldest national park, established by Congress in 1872.
Credit: Richard Taylor/Flickr
A Roosevelt Elk in Yellowstone National Park. The park is widely considered the nation's best habitat for large mammal species, home to free-ranging herds of elk and bison as well as wolves, grizzly bears, bighorn sheep, and the endangered lynx.
Yellowstone's Mammoth Hot Springs. Yellowstone is known for its geothermal features, including geysers, hot springs, and travertine terraces like Mammoth, which are formed when thermal water rises through limestone and forms calcium carbonate deposits on the surface of the rock.
Credit: Adam Jones/Photodisc/Getty
Old Faithful lets off some steam. So-called because of its clockwork eruptions (every 60 to 90 minutes), Old Faithful was the first geyser in Yellowstone to be named and remains the park's most popular. With between 200 and 250 geysers erupting every year, Yellowstone claims the highest concentration of active geysers anywhere in the world.
Credit: Joel Hernandez/Flickr
Travertine at the edge of a hot spring in Yellowstone's West Thumb Geyser Basin
Credit: Carolyn Conner/Flickr
A tranquil sunset in Yellowstone's Hayden Valley
Credit: Phillip Nealey/Digital Vision
An evening sky mirrored in the waters of Yellowstone Lake
Credit: Ron Crabtree/Photographer's Choice
Yellowstone's Grand Canyon isn't as spectacularly deep as its namesake in Arizona, but it certainly doesn't lack for beauty.
Credit: Richard Nowitz/Digital Vision/Getty
Steam rising from the turquoise waters of Yellowstone's Blue Star Spring
Credit: Peter Riveira/Flickr
An eruption at Castle Geyser isn't as easy to catch as one at Old Faithfulthey only occur every 13 hours.