Most agree that Daniel Decatur Emmett wrote “Dixie,” but there is far less certainty as to when and why the South acquired this label.
The most popular theory is that the term was derived from the Mason-Dixon Line. Surveyors Charles Mason and Jeremiah Dixon established this line in 1773 as the boundary between Pennsylvania and Virginia. At that time, slavery was legal in both Pennsylvania and Virginia, but the institution was far weaker in Pennsylvania and facing increasing opposition. In 1780 Pennsylvania adopted a plan for the gradual abolition of slavery, and as a result, the Mason- Dixon Line became the line separating free and slave states.
A second theory traces the term to a Louisiana bank that issued ten-dollar bank notes commonly referred to as Dix (French for ten). Like most bank notes of this period, these Dix notes were only accepted as payment within a limited geographic area—people in New York would not accept a note that had been printed in distant New Orleans. Therefore, “Dixie land” referred to the geographic reach of these bank notes.
Perhaps the most intriguing theory links the label to a mythic Manhattan plantation owner of the early 19th century by the name of Mr. Dixie. Legend has it that slaves were so kindly treated on his plantations that even after they were freed they dreamed of returning to “Dixie Land.”