Mountain States

The Mountain States are a western U.S. region generally comprising Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah, and Wyoming.

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Colorado: A landlocked U.S. state known for the Rocky Mountains and the high-elevation Colorado Plateau. Its Rocky Mountain core is a defining part of the region.
Colorado River: A major river of the American Southwest that supplies water to cities, farms, and ecosystems. Its reservoirs and diversions connect several Mountain States to downstream users.
Indigenous peoples of the Great Basin: The diverse Native peoples whose homelands include the Great Basin of the western United States. Their histories predate state boundaries and remain central to the region’s identity.
Mountain Division: A U.S. Census Bureau division containing the eight states commonly called the Mountain States. It formalizes the same state grouping while distinguishing it from neighboring divisions.
New Mexico: A southwestern U.S. state shaped by deserts, plateaus, and mountain ranges. Its inclusion shows that the region extends into the Southwest.
Colorado River Compact: A 1922 agreement dividing the Colorado River basin’s water between upper and lower basin states. It governs water allocation across states in and beyond the region.
Navajo Nation: A Native American nation whose territory spans parts of Arizona, New Mexico, and Utah. Its land and governance cross state lines within the region.
West North Central States: A U.S. Census Bureau division of seven states in the northern Great Plains and upper Midwest. Its eastern neighbors show how census regions divide the interior West from the Plains.
Great Basin: An arid region of interior drainage spanning much of Nevada and parts of neighboring states. It explains the basin-and-range landscapes across the region’s western states.
Basin and Range Province: A vast region of alternating mountain ranges and desert basins across the western United States. Its terrain underlies much of Nevada and shapes settlement and transport.