US Map / Regions / Mountain

Mountain States Map

Eight states, 856,000 square miles, and about 31 people per square mile — the emptiest Census division in the country.

All 8 Mountain states

The emptiest division in the country: 855,767 square miles of land, about 26.2 million people, roughly 31 per square mile against a national figure near 96. It is also the division with the most federal land — in Nevada and Utah the federal government holds most of the state's surface, which is the single largest fact about how the Mountain West looks and who lives where.

Wyoming is the least populous state in the union at about 588,000. Arizona and Colorado together hold more than half the division's people. Colorado has the highest mean elevation of any state, roughly 6,800 feet, and every one of the eight has land above 10,000 feet.

What the eight actually share

Altitude, aridity, and the rules that follow from them. Every state here allocates water by prior appropriation rather than riparian right, because there was never enough of it; every one has a settlement pattern of a few large metro areas surrounded by very long distances; and every one was a federal territory before it was a state. Six of the eight were admitted in 1889 or later: Montana that year, Idaho and Wyoming in 1890, Utah in 1896, and New Mexico and Arizona in 1912, the last two of the contiguous states. Where the division frays is at the corners: Arizona and New Mexico are usually called the Southwest, Idaho is often lumped with the Pacific Northwest, and Colorado's eastern third is flat plains that have more in common with Kansas than with the Rockies. See the regions hub for how those informal names overlap the official ones.

Cities in the desert and along the Front Range

Phoenix is the fifth-largest city in the United States at about 1.67 million in 2024 and the largest state capital in the country. Its metro area supplies five more top-100 cities — Mesa, Chandler, Scottsdale, Gilbert, and Glendale — which is why Arizona puts seven cities on the national list, more than any other state here. Denver anchors the Front Range corridor with Aurora and Colorado Springs; Las Vegas, Henderson, and North Las Vegas sit in a single valley that holds about three-quarters of Nevada's population. Albuquerque, Tucson, Reno, and Boise complete the list, and Salt Lake City, Billings, and Cheyenne lead the states with no top-100 city.

Geography: the divide, the basin, and the plateau

The Rocky Mountains run the length of the division, carrying the Continental Divide through Montana, Idaho, Wyoming, Colorado, and New Mexico. West of the divide in Nevada and western Utah is the Great Basin, where no water reaches the sea at all; its largest surviving remnant is the Great Salt Lake, and its southern end is the Mojave Desert. The Colorado Plateau covers the Four Corners country, where the Colorado River has cut the Grand Canyon and where Arizona, Utah, Colorado, and New Mexico meet at the only point in the country where four states touch.

The eastern edges of Montana, Wyoming, Colorado, and New Mexico slope away into the Great Plains, and the Rio Grande runs the length of New Mexico from the Colorado line to Texas. The Snake River crosses southern Idaho in a broad volcanic plain that holds most of that state's farmland and population.

Divisions next door

Mountain is the interior half of the West; its sibling is Pacific. East is West North Central in the Midwest and West South Central in the South. Six of the eight states are wholly on Mountain Time; Idaho splits with Pacific at the Salmon River, and Arizona keeps standard time all year except on the Navajo Nation.