The Mountain States (also known as the Mountain West and the Interior West) form one of the nine geographic divisions of the United States that are officially recognized by the United States Census Bureau. It is a subregion of the Western United States.
The Mountain States generally are considered to include: Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah, and Wyoming. The words “Mountain States” generally refer to the US States which encompass the US Rocky Mountains. These are oriented north-south through portions of the states of Montana, Idaho, Wyoming, Colorado, Utah, and New Mexico. Arizona and Nevada, as well as other parts of Utah and New Mexico, have other smaller mountain ranges and scattered mountains located in them as well. Sometimes, the Trans-Pecos area of West Texas is considered part of the region. The land area of the eight states together is some 855,767 square miles (2,216,426 square kilometers).