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, New Mexico, Colorado, Nevada, and Utah are considered part of the southwest.
The division consists of eight states: Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah, and Wyoming. These eight states have the highest mean elevations of all 50 U.S. states. Together with the Pacific States of Alaska, California, Hawaii, Oregon and Washington, the Mountain States constitute the broader region of the West, one of the four regions the United States Census Bureau formally recognizes (the Northeast, South and Midwest being the other three). The word "Mountain" refers to the Rocky Mountains, which run north-south throughout 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.
A butte // is a conspicuous isolated hill with steep, often vertical sides and a small, relatively flat top; buttes are smaller than mesas, plateaus, and table landforms. In some regions, such as the north central and northwestern United States, the word is used for any hill. The word butte comes from a French word meaning "small hill"; its use is prevalent in the western United States, including the southwest, where "mesa" is also used. Because of their distinctive shapes, buttes are frequently landmarks in plains and mountainous areas.
In differentiating mesas and buttes, geographers use the rule that a mesa has a top wider than its height, while a butte's top is narrower. Three classic buttes are Scotts Bluff (actually a collection of five bluffs) in Nebraska, Crested Butte in Colorado, and Elephant Butte in New Mexico.
Among the well-known non-flat-topped buttes in the United States are Bear Butte, South Dakota, and Black Butte, Oregon. In many cases, buttes have been given other names that do not use the word butte, for example, Courthouse Rock, Nebraska. Also, some large hills that are technically not buttes have names using butte, an example of which is Kamiak Butte in Washington State.