Here are some links on importance of Cotton:
http://www.civilwarhome.com/kingcotton.htmIn 1858 Senator James Henry Hammond of South Carolina replied to Senator William H. Seward of New York:
"Without the firing of a gun, without drawing a sword, should they [Northerners] make war upon us [Southerners], we could bring the whole world to our feet. What would happen if no cotton was furnished for three years? . . England would topple headlong and carry the whole civilized world with her. No, you dare not make war on cotton! No power on earth dares make war upon it. Cotton is King."
Hammond, like most white Southerners, believed that cotton ruled not just in the South but in the United States and the world. Many economists agreed. In 1855, David Christy entitled his influential hook Cotton Is King. Cotton indeed drove the economy of the South, affected its social structure, and, during the Civil War, dominated international relations of the Confederacy through "cotton diplomacy."
......
By 1860, cotton ruled the South, which annually exported two-thirds of the world supply of the "white gold." Cotton ruled the West and Midwest because each year these sections sold $30 million worth of food supplies to Southern cotton producers. Cotton ruled the Northeast because the domestic textile industry there produced $100 million worth of cloth each year. In addition, the North sold to the cotton-growing South more than $150 million worth of manufactured goods every year, and Northern ships transported cotton and cotton products worldwide.
and
Cotton and US Civil War
http://mshistory.k12.ms.us/articles/291 ... -civil-war
The diplomatic strategy was designed to coerce Great Britain, the most powerful nation in the world, into an alliance with the Confederacy by cutting off the supply of cotton, Britain’s essential raw material for its dominant textile industry. Before the American Civil War, cotton produced in the American South had accounted for 77 percent of the 800 million pounds of cotton used in Great Britain. After Britain had officially declared its neutrality in the American war in May 1861, the president of the Confederacy, Jefferson Davis – a Mississippi planter, Secretary of War under U.S. President Franklin Pierce, and former U. S. senator – strongly supported what became known as King Cotton diplomacy. Confederate leaders believed an informal embargo on cotton would lead Great Britain into formal recognition of the Confederacy and to diplomatic intervention with other European countries on behalf of the South.
To begin King Cotton diplomacy, some 2.5 million bales of cotton were burned in the South to create a cotton shortage. Indeed, the number of southern cotton bales exported to Europe dropped from 3 million bales in 1860 to mere thousands. The South, however, had made a pivotal miscalculation. Southern states had exported bumper crops throughout the late 1850s and in 1860, and as a result, Great Britain had a surplus of cotton. Too, apprehension over a possible conflict in America had caused the British to accumulate an inventory of one million bales of cotton prior to the Civil War. The cotton surplus delayed the “cotton famine” and the crippling of the British textile industry until late 1862. But when the cotton famine did come, it quickly transformed the global economy. The price of cotton soared from 10 cents a pound in 1860 to $1.89 a pound in 1863-1864. Meanwhile, the British had turned to other countries that could supply cotton, such as India, Egypt, and Brazil, and had urged them to increase their cotton production. Although the cotton embargo failed, Britain would become an economic trading partner.
.....
America regained its sought-after position as the world’s leading producer of cotton. By 1870, sharecroppers, small farmers, and plantation owners in the American south had produced more cotton than they had in 1860, and by 1880, they exported more cotton than they had in 1860. For 134 years, from 1803 to 1937, America was the world’s leading cotton exporter.
from: Economics of the Civil War
----------
I think the price of cotton rose after 1857 and the profits spurred the South to secede from the Union.