Let's analyze each statement:
A) 50% of Southern families owned slaves. - This statement is incorrect. The percentage of Southern families who owned slaves before the Civil War was actually around 25% to 30%.
B) 6% of Blacks in the South were not slaves. - This statement is also incorrect. By the time of the Civil War, approximately 10% of the Black population in the South were free, not just 6%.
C) Most Southern middle class lived in the countryside. - This statement is generally true. The Southern middle class often included small farmers and tradespeople who primarily lived in rural areas.
D) Most Northern elites were wealthy plantation owners. - This statement is incorrect. Most Northern elites were involved in industrial and commercial enterprises, not plantation ownership, which was primarily a Southern phenomenon.
Therefore, the CORRECT statement is C) Most Southern middle class lived in the countryside.