The United States is divided into regions based on geography, culture, history, and economic factors. The most commonly used classification system is the one defined by the United States Census Bureau, which groups the 50 states and the District of Columbia into four regions and nine divisions based on geographic proximity. The four regions are:

• Northeast: Includes Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, and Vermont.

• Midwest: Includes Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, and Wisconsin.

• South: Includes Alabama, Arkansas, Delaware, District of Columbia, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, and West Virginia.

• West: Includes Alaska, Arizona, California, Colorado, Hawaii, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming.

Other unofficial regions are also recognized, such as New England, the Great Plains, and the Southwest.