The State of Wyoming 's a state in the Western United States. The majority of the state's dominated by the mountain ranges and rangelands of the Rocky Mountain West, while the easternmost section of the state includes part of a high altitude prairie region known as the High Plains. While the tenth largest U.S. state by size, Wyoming's the least populous, with a U.S. Census estimated population of 522,830 in 2007, a 5.9% increase since 2000. The capital and the most populous city of Wyoming's Ch… (More on Wyoming)