The south starts below the Mason-Dixon line...everything below Pennsylvania. Back during the Civil War and times of Slavery, Delaware & Maryland were both in between....border states....like Delaware fought in the union eventhough slaves were in abundance there. Even today, the northern part of Delaware is real urban while the southern half is rural as fukk. Then with Maryland, alot of abolitionists were from there. Harriet Tubman, Frederick Douglass....by just traveling the 100 or so miles from Maryland to Philadelphia, they were considered out of the south and free
So yea...
But in modern day, atleast to me.....the South starts after Washington, D.C. Once you head into Northern Virginia and all points southward, that's the south.