Which major economic developments intensified Southern states" political power and economic influence over the U.S. government prior to the Civil War? The land acquisition from the Louisiana Purchase Links to an external site.in 1803 greatly expanded the territory available for plantation agriculture. Eli Whitney's "invention" of the cotton gin Links to an external site.in 1793 greatly reduced the time and labor required to pick a pound of cotton. The emergence of the cotton textile industry Links to an external site.in England created a demand for U.S.-produced cotton. A & B All of the above