Established in 1872, Yellowstone National Park is America's first, extending through Wyoming, Montana, and Idaho. The park's name is derived from the Yellowstone River, which runs through the park.
At Yellowstone, steam from the hot springs fills the air around the Midway Geyser Basin, home of Grand Prismatic.
The geothermal pool in Yellowstone National Park in Wyoming. (Oct. 8, 2012)
A juvenile grizzly bear wanders the grounds near the Fishing Village Visitor Center.
Tourists watch Old Faithful erupt, which the geyser does an average of every 90 minutes, at Yellowstone National Park, in Wyoming. (June 1, 2011)
Mammoth Hot Springs has been described as "geology in overdrive" because of the way the travertine steps change color and shape so often.
A small herd of buffalo drinks from a pond in Yellowstone National Park, in Wyoming. (Oct. 9, 2012)
Beehive Geyser in Yellowstone National Park in Wyoming. Yellowstone has about 300 geysers and 10,000 hot springs, bubbling mudpots and steam vents. (Sept. 2009)
A herd of bison crosses the road in Yellowstone. During peak months, a bison crossing can snarl traffic for miles.
Visitors use spotting scopes to try to catch a glimpse of the wolves and other wildlife at Hayden Valley.
The Lower Falls of Yellowstone plunge 308 feet. The green stripe is from a notch at the lip of the falls, making the water deeper at that point where it's not as turbulent.
A rainbow arcs over the canyon at the Lower Falls of the Yellowstone River in Yellowstone National Park.
Elk congregate by the chief concessionaire's residence at Mammoth Hot Springs in Yellowstone National Park.
River otters huddle near Pelican Creek in Yellowstone National Park, in Wyoming. (Oct, 9, 2012)
A wily coyote runs down the road in Yellowstone National Park in Wyoming. (Oct. 8, 2012)
A bald eagle in Yellowstone National Park in Wyoming. (Oct. 8, 2012)
A view of the Sunset Lake in the Yellowstone National Park in Wyoming. (June 1, 2011)