the early 2000s, there were estimates of as much as 2.2 trillion cubic feet of natural gas below the front in Montana, although only 200 billion cubic feet was available on leasable land. By 2003, much of the Rocky Mountain Front in the state consisted of land owned by the U.S. federal government and managed by the United States Forest Service and the federal Bureau of Land Management (BLM). By one count, BLM alone managed of land on the Rocky Mountain Front in the state. Beginning in 2001, petroleum exploration was banned for a six-year period on Forest Service land in the front. In the fall of 2002, BLM issued new regulations making it easier to engage in oil and gas production along the Montana front. Conservationists have actively worked to protect the region from energy exploration. Wyoming Southwest Wyoming, where the borders of Idaho, Utah, and Wyoming come together, is another area where the Cordilleran foreland thrust-and-fold remains largely intact. (The other is northwest Montana, as noted above.) The Rocky Mountain Front in Wyoming is believed to have extensive oil and natural gas reserves. In the late 1970s, the U.S Forest Service and Bureau of Land Management attempted to open these lands to energy exploration. This led to extensive litigation and changes in federal land use regulations. Colorado In Colorado, the Rocky Mountain Front extends from the west-northcentral part of the border with Wyoming south to the city Pueblo and the Arkansas River. Peaks within the front include Pikes Peak, Mount Evans, and Longs Peak. Just east of the Rocky Mountain Front is the Colorado Piedmont, and within the Piedmont is the most heavily urbanized part of the United States between Chicago and the West Coast. The only pass through the Rocky Mountains in the area is the Tennessee Pass. The Rocky Mountain Front forms the eastern boundary of a triangular area of volcanic activity centered on western Colorado. Several sandstone horizons underlie the Colorado Rocky Mountain Front as well, and decline steeply to the east. In popular culture "The Rocky Mountain Front" is the title of an essay by noted Montana author A. B. Guthrie, Jr. It first appeared in Montana, The Magazine of Western History in 1987. References Bibliography Baron, Jill. Rocky Mountain Futures: An Ecological Perspective. Washington, D.C.: Island Press, 2002. Benson, Jackson J. Under the Big Sky: A Biography of A.B. Guthrie Jr. Lincoln, Neb.: