The Southern United States (sometimes Dixie, also referred to as the Southern States, the American South, the Southland, Dixieland, or simply the South) is one of the four census regions defined by the United States Census Bureau. It is between the Atlantic Ocean and the Western United States, with the Midwestern and Northeastern United States to its north and the Gulf of Mexico and Mexico to its south.
Historically, the South was defined as all states south of the 18th-century Mason–Dixon line, the Ohio River, and the 36°30′ parallel. Within the South are different subregions such as the Southeast, South Central, Upper South, and Deep South. Maryland, Delaware, Washington, D.C., and Northern Virginia have become more culturally, economically, and politically aligned in certain aspects with the Northeastern United States and are sometimes identified as part of the Northeast or Mid-Atlantic. The U.S. Census Bureau continues to define all four places as formally being in the South. To account for cultural variations across the region, some scholars have proposed definitions of the South that do not coincide neatly with state boundaries. The South does not precisely correspond to the entire geographic south of the United States, but primarily includes the south-central and southeastern states. For example, California, which is geographically in the southwestern part of the country, is not considered part of the South; however, the geographically southeastern state of Georgia is.