Answer:
The institution of slavery.
Explanation:
Slavery was not needed in the north because due to cold weather poor soil the Northerners depended on trade and manufacturing but in south the soil was fertile and plantation system was rampant so slave labour was utilised on tobacco and cotton farms.
Some of the large plantations had more than 200 slaves and there were laws that barred the slaves for earning their freedom, receiving education and freedom.
The planters depended on the slave labour because indentured labour became expensive, they tried to use the Natives American but they didn't had immunity to the European diseases hence perished in large numbers. while the African slaves had immunity against such diseases.
