In what region of the early United States was indigo a cash crop?

In Colonial America, South Carolina was known as the main growing location of indigo.

As the second half of the eighteenth century wore on, indigo continued to be grown in ever larger numbers. In the year 1775, some 1,122,200 pounds were exported from South Carolina. Yet, South Carolina's dependence upon governmental bounties in order to preserve indigo's prosperity proved to be dangerous. Although indigo continued to be produced during the Revolution, after the Treaty of Paris in 1783, the bounties and protective tariffs were no longer valid. Thus, Carolina indigo had to compete on the open market. Until the mid 1790's, indigo continued to sell well because Britain needed it for its textile industry. However, the loss of the bounty, indigo competition from India, and the 1793 invention of the cotton gin caused indigo to be almost completely phased out of South Carolina by 1798. When British legislation no longer effected the indigo grown in America, the "Bonanza" went bust.