Yellowstone, the first national park in the world, was established by the U.S. Congress in 1872 and has welcomed millions of visitors in the 139 years since. Last year, Yellowstone recorded its highest number of visitors ever, as some 3.6 million people passed through its gates. Its well-known geothermal features -- geysers, hot springs, and fumaroles -- owe their existence to the massive Yellowstone Caldera, a 45-mile-wide volcanic system beneath the park. Tourists are also drawn to Yellowstone's hundreds of species of wildlife, massive waterfalls, and incredible vistas. Collected below are a few recent views of Yellowstone National Park. [41 photos]
A gray wolf and its nursing pups are pictured in Yellowstone National Park in this photograph obtained on May 4, 2011. Federal protections for some 1,200 gray wolves in Montana and Idaho officially ended on May 5, under unprecedented legislation passed by Congress last month removing them from the endangered species list.
(Reuters/National Park Service) #
Sunset Lake hot spring, lined with unique colors caused by multicolored algae-like bacteria called thermophiles that thrive in the cooling water, turning the vivid aqua-blues to a murkier greenish brown. Photographed in Yellowstone National Park, on June 1, 2011.
(Mark Ralston/AFP/Getty Images) #