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 are usually split up into two other regions known as the Northwest and Southwest. Idaho, Montana, and Wyoming are considered part of the Northwest, while Arizona, Colorado, Nevada, New Mexico, and Utah are considered part of the Southwest.