Answer:
Slavery enabled the large plantation owners to grow extremely wealthy, therefore creating the sort-of aristocratic upper-class of the south. Those with less slaves therefore made less money, and had less status. Those who lacked slaves completely, such as the yeoman farmers, made up the lowest classes of free whites, because of whites they were the most power. Finally below them were freed blacks, who, because of the racism instilled by the institution of slavery, were cast out of society even if they were rather successful on their farms.
Hope this helps.