With the introduction of the cotton gin in the 1790s, the county's economic prospects increased as the importance of "King Cotton" grew, and slavery became an integral part of the economy. In 1800, 25% of all white families in the Upcountry owned slaves, but by 1820 nearly 40% were slaveholders. Slave ownership increased significantly in York County between 1800 and 1860, though most slaves worked on small and medium-sized farms rather than larger plantations. In 1800, whites made up 82.10% of the total population in York County, but by 1860 the white percentage of the total population had dropped to 62.50%. Figures from 1860 reveal slave holdings in York County were relatively small, with approximately 70% of all farms holding fewer than 10 slaves and less than 3% of the farms with 50 or more.