… the Midwest …
The Midwest consists of Ohio, Michigan, Indiana, Wisconsin, Illinois, Minnesota, Iowa, Missouri, North Dakota, South Dakota, Nebraska, and Kansas.
… the South …
The South claims more states than any other region: Delaware, Maryland, Virginia, West Virginia, Kentucky, North Carolina, South Carolina, Tennessee, Georgia, Florida, Alabama, Mississippi, Arkansas, Louisiana, Texas, and Oklahoma.
Washington, DC, is also included in the South, according to the Census Bureau.
Related: Why no one can agree on where the South really is
… and the West.
The West comprises Montana, Idaho, Wyoming, Colorado, New Mexico, Arizona, Utah, Nevada, California, Oregon, Washington, Alaska, and Hawaii.
But that's not the only way to divide up the country. Several federal agencies use this map of the 10 "Standard Federal Regions" drawn up by the Office of Management and Budget.
Some of the agencies that use the OMB's map are the Environmental Protection Agency and the Department of Health, Education, and Welfare.
No one said regions had to be culturally similar. Time zones count too, and the US is divided into six of them.
The four time zones in the contiguous US are Eastern, Central, Mountain, and Pacific. Alaska and Hawaii each have their own time zones, too.
The US federal courts system divides the US into 11 regions, each one containing a US court of appeals.
There are 13 courts of appeals in total — the federal court and the DC court, representing the nation's capital, are the other two.
The Federal Reserve splits up the US into 12 districts, each containing a Federal Reserve Bank.
The Federal Reserve Banks are located in Boston, New York City, Philadelphia, Richmond, Atlanta, Chicago, Cleveland, Minneapolis, Kansas City, St. Louis, Dallas, and San Francisco.
The Bureau of Economic Analysis goes with this eight-region map of the US. Its regions are New England, the Mideast, the Southeast, the Great Lakes, the Plains, the Southwest, the Rocky Mountains, and the Far West.
The BEA uses this map to compare economic data between regions.
Lastly, the Petroleum Administration for Defense uses this map of five regions, originally drawn up in 1942 to ration the country's gasoline.
It's no wonder it's so hard to say, once and for all, which states are in which regions.
The South in particular tends to be up for debate.