Mountain states
One of nine U.S. Census divisions, encompassing the Rocky Mountains.
The Mountain states, also known as the Mountain West or the Interior West, form one of the nine geographic divisions of the United States officially recognized by the United States Census Bureau. They are a subregion of the Western United States, comprising Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah, and Wyoming. The region is defined by the presence of the U.S. Rocky Mountains, which run north-south through portions of Montana, Idaho, Wyoming, Colorado, Utah, and New Mexico, with other smaller mountain ranges and scattered mountains in Arizona and Nevada. The region is the fastest-growing in the country, with several of its states ranking among the fastest-growing nationally; its largest city is Phoenix. Subregions include the Southwest (Arizona, New Mexico, southern Nevada, and far West Texas), the Intermountain region (Utah, Nevada, Idaho, and parts of other states), and the Front Range region (northern New Mexico, Colorado, and southeast Wyoming). The terrain is exceptionally diverse, ranging from the highest mountain peaks in the continental United States to large deserts and rolling plains. The Great Basin Desert covers nearly all of Nevada, western Utah, and southern Idaho. The Mojave Desert lies mostly in southern Nevada, while the Sonoran Desert occupies much of Arizona and the Chihuahuan Desert covers most of southwestern and southern New Mexico. Colorado has scattered desert lands in its southern and northwestern parts, including the San Luis Valley, the world’s largest high-altitude valley desert. The eastern portion features the High Plains, a high-elevation, low-rainfall area of flat rolling land with buttes, canyons, and forests. The climate is predominantly semi-arid or arid, with alpine climates in the mountains. Some high peaks receive heavy snow and rain, while other areas receive very little precipitation. Northern and northeastern Arizona exhibit a high desert climate with hot, dry summers and cold, snowy winters.
- States included
- Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah, Wyoming
- Largest city
- Phoenix
- Fastest-growing region
- Yes, in the United States
- Highest mean elevation
- Among all 50 U.S. states
- Primary time zone
- Mountain Time (except Nevada and Idaho Panhandle, which observe Pacific Time)
Lore & Background
The Mountain states encompass Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah, and Wyoming, with the Trans-Pecos area of West Texas occasionally included. This region is defined by the north-south orientation of the Rocky Mountains, which run through portions of Montana, Idaho, Wyoming, Colorado, Utah, and New Mexico; Arizona and Nevada, along with other parts of Utah and New Mexico, contain smaller mountain ranges and scattered peaks. The terrain is exceptionally diverse, ranging from some of the highest mountain peaks in the continental United States to vast deserts and rolling plains. The Great Basin Desert covers nearly all of Nevada, western Utah, and southern Idaho. The Mojave Desert extends into southern Nevada, while the Sonoran Desert occupies much of Arizona, and the Chihuahuan Desert covers most of southwestern and southern New Mexico. Colorado has scattered desert lands in its southern and northwestern parts, including the San Luis Valley, the largest high valley desert in the world. The Colorado Plateau contributes additional desert areas, such as the Painted Desert in northern Arizona and the San Rafael Desert in eastern Utah. The far-eastern portion of the region features the High Plains, a section of the Great Plains with flat, rolling land, buttes, canyons, and forests, sitting at elevations of 3,000 to 6,000 feet. The climate is generally semi-arid or arid, with alpine climates in the mountains; some high peaks receive heavy snow and rain, while other areas get very little precipitation. The southern parts of Nevada and Arizona often see little to no snow, while northern Nevada and higher elevations in Arizona can receive substantial snowfall. The region is the fastest-growing in the United States, with Phoenix as its largest city.
Reader's Guide
The Mountain states are one of the largest and most diverse regions in the United States. Its physical geography ranges from some of the highest mountain peaks in the continental United States to large desert lands and rolling plains in the eastern portion of the region. The Great Basin Desert is located in almost all of Nevada, western Utah, and southern Idaho. Portions of the Mojave Desert are located in southern Nevada, the Sonoran Desert in much of Arizona, and the Chihuahuan Desert in most of southwestern and southern New Mexico. The High Plains, a portion of the Great Plains, lie in the far-eastern portions of the region. The climate is generally semi-arid or arid, with alpine climates in the mountains. The region is the fastest-growing in the United States, with Utah, Idaho, Nevada, Colorado, and Arizona ranking among the fastest-growing states. The Phoenix metropolitan area is the most populous metropolitan area, followed by Denver, Las Vegas, and Salt Lake City.
Did You Know?
- The Mountain states are one of nine geographic divisions officially recognized by the United States Census Bureau.
- Phoenix is the largest city in the Mountain states.
- Daylight saving time is not observed in Arizona, except for lands within the Navajo Nation.
Frequently Asked Questions
What exactly are the "Mountain states" in U.S. geography?
It is one of the nine official geographic divisions the U.S. Census Bureau uses to organize the country. The division sits within the broader Western United States and takes its name from the Rocky Mountain range that threads through its core.
What time zone do people in the Mountain states live in?
Most of the region follows Mountain Time, but Nevada and the northern panhandle of Idaho are the exception, observing Pacific Time instead.
Why do geographers and fans find the Mountain states region notable?
It holds the highest average elevation of any U.S. state grouping and is currently the fastest-growing region in the country. Its landscape is dominated by the north-south spine of the Rockies plus smaller ranges scattered through Arizona and Nevada.
What is the largest city in the Mountain states?
Phoenix, Arizona, holds that title as the most populous city across all eight states in the division.
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