Wyoming is a U.S. state. It is the least populous state, with around 400,000 people, due to its mountainous territory, primarily the Rocky Mountains. Wyoming borders Montana to the north, Idaho to the west, Utah and Colorado to the south, and Nebraska and South Dakota to the east. Wyoming is home to Yellowstone National Park, one of the most popular national parks in the country. Wyoming's capital, Cheyenne, is also its largest city, with around 50,000 people.