The first crop that formed the basis of the economy in the Southern states was tobacco. But at the beginning of the 19th century cotton became the most important. During the 1840s and 1850s cotton became the chief United States export. It was known as "King cotton". The rapid agricultural growth of the South led to financial and political tensions between the Northern and the Southern states. Answer: The most important Southern crop in the 1840s and 1850s was cotton.
