The Deep South is a descriptive category of the cultural and geographic subregions in the American South

Southern United States

The Southern United States—commonly referred to as the American South, Dixie, or simply the South—constitutes a large distinctive area in the southeastern and south-central United States...

. Historically, it is differentiated from the "Upper South" as being the states which were most dependent on plantation type agriculture during the pre-Civil War

American Civil War

The American Civil War was a civil war fought in the United States of America. In response to the election of Abraham Lincoln as President of the United States, 11 southern slave states declared their secession from the United States and formed the Confederate States of America ; the other 25...

 period. The Deep South was also commonly referred to as the Lower South or the "Cotton States".

Today, the Deep South is usually delineated as being those states and areas where things most often thought of as "Southern" exist in their most concentrated form.
The term "Deep South" is defined in a variety of ways:

• Most definitions include the states of Alabama
  Alabama
  Alabama is a state located in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east, Florida and the Gulf of Mexico to the south, and Mississippi to the west. Alabama ranks 30th in total land area and ranks second in the size of its inland...
  
  , Georgia
  Georgia (U.S. state)
  Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...
  
  , Louisiana
  Louisiana
  Louisiana is a state located in the southern region of the United States of America. Its capital is Baton Rouge and largest city is New Orleans. Louisiana is the only state in the U.S. with political subdivisions termed parishes, which are local governments equivalent to counties...
  
  , Mississippi
  Mississippi
  Mississippi is a U.S. state located in the Southern United States. Jackson is the state capital and largest city. The name of the state derives from the Mississippi River, which flows along its western boundary, whose name comes from the Ojibwe word misi-ziibi...
  
  , and South Carolina
  South Carolina
  South Carolina is a state in the Deep South of the United States that borders Georgia to the south, North Carolina to the north, and the Atlantic Ocean to the east. Originally part of the Province of Carolina, the Province of South Carolina was one of the 13 colonies that declared independence...
  
  .
• The seven states
  Confederate States of America
  The Confederate States of America was a government set up from 1861 to 1865 by 11 Southern slave states of the United States of America that had declared their secession from the U.S...
  
   that seceded from the United States
  United States
  The United States of America is a federal constitutional republic comprising fifty states and a federal district...
  
   before the firing on Fort Sumter
  Fort Sumter
  Fort Sumter is a Third System masonry coastal fortification located in Charleston Harbor, South Carolina. The fort is best known as the site upon which the shots initiating the American Civil War were fired, at the Battle of Fort Sumter.- Construction :...
  
   and the start of the American Civil War
  American Civil War
  The American Civil War was a civil war fought in the United States of America. In response to the election of Abraham Lincoln as President of the United States, 11 southern slave states declared their secession from the United States and formed the Confederate States of America ; the other 25...
  
  , and originally formed the Confederate States of America
  Confederate States of America
  The Confederate States of America was a government set up from 1861 to 1865 by 11 Southern slave states of the United States of America that had declared their secession from the U.S...
  
  .