Where: Western United States

What's at stake: Some of the largest expanses of undeveloped wilderness in the lower 48 states; important wildlife habitat

Threatened by: Oil and gas development

Animals include: Buffalo, gray wolf, grizzly bear, elk, pronghorn antelope, bighorn sheep, lynx, Yellowstone cutthroat trout

	In the United States, the Rocky Mountains extend from Montana to New Mexico. The highest peak in the range -- and the second highest peak in the lower 48 states -- is Mount Elbert in Colorado, which rises 14,433 feet above sea level.
	Montana's Rocky Mountain Front -- which runs through Glacier National Park -- is home to one of the country's largest bighorn sheep herds. During rutting season, males use their horns in fierce jousting sessions, the sounds of which can echo more than a mile away.
	The northern Rockies are also one of the last refuges of the remaining 1,000 or so grizzly bears in the contiguous United States. Prior to European settlement, 50,000 to 100,000 of these majestic creatures roamed the American West.
	Encompassing an area roughly the size of West Virginia, the greater Yellowstone ecosystem is among the largest relatively intact temperate-zone ecosystems on earth. Its vast quilt of public lands includes two national parks (Yellowstone and Grand Teton), three national wildlife refuges and parts of seven national forests.
	The Yellowstone region boasts an abundance of wildlife, including the world's largest elk herd and one of the few, free-roaming buffalo herds. This rugged landscape also serves as a winter nesting ground for trumpeter swans, whose snow-white wings can span seven feet.
	As late as 1850, roughly 100,000 grizzly bears lived between Canada and Mexico, ranging from the Pacific Coast to the Mississippi River. Today, only about 1,000 can be found in that area -- all in Greater Yellowstone and four other isolated pockets of still-wild high country. An estimated 350 to 600 bears live in and around Yellowstone National Park, with another 300 to 400 in Glacier National Park.
	Grizzlies in the lower 48 states were among the first animals to be protected under the federal Endangered Species Act in 1975, and their listing is credited with preventing their complete disappearance from the Northern Rockies.
	To survive, grizzlies need large areas of wild country and isolation: in Yellowstone, the home range of a typical adult female covers some 450 square miles, while an adult male covers twice that area. Over the years grizzly habitat has been destroyed, degraded and fragmented by energy development, mining, sprawl, roads, and off-road vehicle use.
	In southwestern Wyoming, the Red Desert is home to 45,000 pronghorn antelope - one of the largest herds in the lower 48 states. The pronghorn, also known as the prairie ghost, is the fastest land mammal in North America, reaching speeds of up to 60 miles per hour.
	The Red Desert is also known for pre-historic rock art and towering buttes such as Boar's Tusk, an ancient volcanic formation that rises sharply from the desert floor and is considered sacred by the Shoshone tribe.
	Vermilion Basin, an undisturbed area of desert canyons and woodland plateaus in northwestern Colorado, is home to spectacular petroglyphs (rock carvings), including one that's six feet high.
	South of Vermillion Basin, the Hermosa Creek watershed in the San Juan National Forest marks the largest stretch of roadless wilderness in the southern Rockies. The watershed, which is studded with old-growth ponderosa pines, provides a corridor for wildlife between two neighboring valleys.

Photo credits: Bear grass and moon at twilight, © Randy Beacham. Bison with calf, © Laura Romin & Larry Dalton, Wildlife Reflections Photography.