trade, cotton had made the South quite powerful, but it depended on constant production of new cotton. 

To address this demand, the cotton gin opened up the drier upland soils by allowing high quality cotton to come from lesser quality plants in lesser quality locations. The gin also encouraged smaller cotton farms that required more manual labor. So cotton production continued to soar and to spread from wealthy coastal landowners to smaller hardscrapple farmers. They often didn't own their own gins, so they were at the mercy of the major merchants who bought and ginned their raw cotton. 

See where this is headed? The South developed a dependence on one crop, which increasingly was controlled by merchants and wealthy coastal landowners. The majority of the cotton farmers did not do as well, but were so dependent on cotton that they willingly became foot soldiers when the Civil War began, so as to protect their livelihood and smaller farms. The gin allowed the production of high quality cotton from low quality raw product, which then allowed cotton to be grown elsewhere. South America, India, and other countries began to compete with the South and the trading strength of the South began to weaken. Ultimately, this was a bad economic model, and the fact that the short-staple cotton required more slaves -- a hot point with the North and with some of their European trading partners -- caused the position of the South to weaken. Before they knew it, they were initiating a Civil War but had lost the trading clout they had counted on and ended up sending their upland cotton farmers into battle. It became very bloody and the South was divided within itself between the coastal barons of Savannah and Atlanta and the inland farmers. Ultimately, trade drove change in cotton, the spread of the cotton gin, the spread of slavery, and the simultaneous weakening of trade links with Europe. The South doomed itself by its efforts to expand in the cotton trade with lower grade cotton, and the Civil War was lost before it started. The economic desolation of the South after the Civil War came about because the trade was disrupted long enough and had already been weakening, so even if slavery hadn't been abolished, the heyday of cotton was over and all these cotton growers had nothing to live on. 

The crops grown on plantations and the slavery system changed significantly between 1800-1860. This occurred for a few reasons. In the early 1800s, plantation owners grew a variety of crops. These crops included tobacco, hemp, wheat and vegetables in the Upper South. In the Deep South, plantation owners grew cotton, sugar, and rice. Cotton could be profitable, but there was a very limited area where long stable cotton could be grown. With this cotton, machines could easily separate the seeds from the cotton. Short staple cotton could be grown inland. However, the seeds had to be separated by hand. This was very difficult to do. Slaves were used to do work on all of these plantations. However, the invention of the cotton gin totally changed things in the south. The cotton gin was a machine that made it much easier to separate the seeds from short staple cotton. Since there was a lot of land available inland, plantation owners could now grow lots and lots of cotton. This would allow them to make a lot of money. Thus, slavery became much more important. It is questionable if slavery would have spread if the cotton gin wasn’t invented. Now, because demand for cotton was high worldwide, the plantation owners needed slaves more than ever. They could make a lot more money by selling cotton. By 1860, cotton was the main export of the south. Thus, the invention of the cotton gin and high demand for cotton changed the kinds of crops grown in the south and increased the need for slaves.