Ix - In 1790 there were six slave states; in 1860 there were 15. - From 1790 until Congress banned the importation of enslaved people Africa in 1808, Southerr - By 1860 approximately one in three Southerners was enslaved. Which event played the GREATEST role in creating these conditions in the South during the Antebel A the Northwest Ordinance of 1789 B the Dred Scott decision of 1857 C the secession of South Carolina in 1860 D the invention of the cotton gin by Eli Whitney in 1793