Eli Whitney's invention of the cotton gin in 1793, cotton became very profitable. However, at the same time the increase in the number of plantations willing to move from other crops to cotton meant the greater need for a large amount of cheap labor, slaves. The southern economy became a one crop economy, depending on cotton and on slavery. On the other hand, the northern economy was based more on industry than agriculture. The northern industries were purchasing the raw cotton and turning it into finished goods. This disparity between the two set up a major difference in economic attitudes.