Why was slavery important to the South?

Cheap free labor was the only way of producing cotton - and lots of it. Following the invention of the cotton gin, cotton become "king" in the South, comprising a majority of its exports. Without slavery, cotton could not be harvested, and the large plantation holders would surely be in ruins. Though the owners of huge plantations did not amass to a majority in the South, they were the political leaders and drove the economy. For the economic and political success of both the South and the plantation owners, the institution of slavery had to continue.