Slave trade was one of the most popular businesses in the world since the first century until the 19th century. United States had a large percentage of slave people working in the cotton plantation. But in the late 17th century and the beginning of the 18th century, this business received a lot of criticism from human right groups, which led to the united states passing laws which prohibited slave trade. The business became unpopular hence people were not forced to provide labor in the plantation, thus the number of slave labor reduced drastically.
Landowning, business, religious and/or political forces came out with one voice and laid down laws the mitigated slave labor. This region becomes the first to abolish slavery and by mid 18th century it became a free slave state.