South vs Southern United States

South

name
  • The south-eastern states of the United States, including many of the same states as formed the Confederacy. 

  • The Global South. 

  • A surname. 

  • Those states which formed the Confederacy during the American Civil War. 

  • The southern part of any region; alternative letter-case form of south. 

Southern United States

name
  • An expansive region encompassing the southeastern and south-central part of the United States, typically defined as including the states of Texas, Oklahoma, Louisiana, Arkansas, Alabama, Mississippi, Tennessee, Kentucky, Florida, Georgia, North Carolina, South Carolina, West Virginia, and Virginia, sometimes also Maryland, Delaware, Washington, D.C., and Missouri. 

How often have the words South and Southern United States occurred in a corpus of books? (source: Google Ngram Viewer )