Why did the cotton gin cause the plantation system to expand?
The cotton gin increased the area where cotton could be commercially grown.
Before the cotton gin only long stem cotton could be commercially grown. The areas where long stem cotton could be grown were limited to areas that were cooler such as Virginia, North Carolina, and upstate Georgia and South Carolina.
Short stem cotton could be grown in a much larger geographical areas such as all of Georgia, low land Virginia, North and South Carolina , Mississippi , Lousiana, Texas and Arkansas. With the use of the cotton gin the short stem variety of cotton could be commercially turned into cloth.
New plantations were started across the south after the invention of the cotton gin. Plantations were started where plantations were not variable previously. The growth of the the plantation culture increased the demand for slaves to work the new plantations.