“King cotton” was an expression of the mid-1800s, when cotton had become so vital to the economies of southern states that it was said to rule them. Until the 1790s growers were limited to producing the quantity of cotton that could be processed by slaves. Separating cotton’s fibers from its seeds was a time-consuming and labor-intensive process: the bolls were dried in front of a fire, and the seeds were picked out by hand. In 1793 American inventor Eli Whitney (1765–1825) introduced the cotton gin. In one day, his machine could clean 50 times as much cotton fiber than could a manual laborer. While Whitney patented the machine in 1794, imitations were nevertheless quickly put into production by shrewd businessmen who observed the effect the gin could have on the nation’s cotton industry. There was no shortage of demand for the fiber. Just before Whitney developed the gin, another inventor, British-born Samuel Slater (1768–1835), built the first successful water-powered machines for spinning cotton, which he introduced at a Rhode Island mill in 1790. As the 1800s dawned, machinery had made cotton the center of the nation’s emerging textiles industry.

Growers in the South stepped up cotton production to keep up with factories’ demands. Slave labor and excellent growing conditions in the southern states (predominately Alabama, Mississippi, Georgia, and South Carolina) combined to dramatically increase production. By 1849 cotton exports reached $66 million a year and accounted for roughly two-fifths of total U.S. exports. But cotton came at a dear price. While laborers in the North’s textile factories worked under difficult and sometimes dangerous circumstances, in the South cotton crops were planted and harvested by slaves. As abolitionists became increasingly vocal about the immorality of slavery and demanded the U.S. government legislate the abolition of slavery, southern growers defended the system, knowing that their livelihoods and the South’s economy depended on it. In 1858 Senator James Henry Hammond (1807–1864) of South Carolina taunted northern sympathizers, saying, “You dare not make war on cotton—no power on earth dares make war upon it. Cotton is king.” Hammond was not the first to use the phrase; it was coined three years earlier in the title of a book. Cotton’s importance to the South contributed to the deepening North-South divide in the nation. By the time the Civil War (1861–65) began, the southern United States supplied two-thirds of the world’s cotton.