Soon after Georgetown was established, the Indian trade declined. Many traders made longer trips to the interior of the upper rivers, for instance to Cherokee Country. In the Lowcountry, planters developed large plantations and cultivated indigo as the cash commodity crop, with rice as a secondary crop. Both were labor-intensive and dependent on enslaved Africans and African Americans, the former imported from Africa in the Atlantic slave trade. Agricultural profits were so great between 1735 and 1775 that in 1757 the Winyah Indigo Society, whose members paid dues in indigo, opened and maintained the first public school for white children between Charles Town and Wilmington. By the early 19th century, rice replaced indigo as the chief commodity crop. It became a staple of regional diets as well, marking a unique characteristic of this area.