The Southern United States (also known as The Southern States or "The South" among Americans) is a term for the Southeastern part of the United States. All Confederate States were in the South, but not all Southern States joined the Confederacy. The States farthest to the south are called the "Deep South". Even though Arizona, New Mexico and southern California are geographically southern parts of United States, they are usually classified as the Southwestern United States and not the South.