William Alston was born in South Carolina around 1756 or 1757 into the wealthy Alston family of the Lowcountry. The precise date and details of his parents are not consistently presented in readily available biographical summaries. He grew up within the rice-plantation economy around Georgetown, a region where immense fortunes were created by the coerced labor and specialized knowledge of enslaved Africans and African Americans.

As the son of a planter family, Alston’s education would have prepared him for estate management, horsemanship, accounts, law and politics at a practical level, and the social obligations of a provincial gentleman. No source consulted identifies a particular school or tutor, so a more exact educational claim would be speculative. His youth was shaped by rivers, tidal rice fields, coastal trade, and the militia system through which white landowners exercised local authority.

When the Revolution became a civil war in South Carolina, Alston joined the Patriot side. He served as a captain and became associated with Francis Marion, the partisan commander whose small mounted forces operated through swamps, plantations, and back roads after the British captured Charleston in 1780. Later accounts describe Alston as an aide or officer under Marion. This service demanded local geographic knowledge, the ability to mobilize men and horses, and navigation among communities divided between Patriots, Loyalists, and people attempting to survive both armies.

The war formed the decisive passage from Alston’s youth into adult prominence. After peace, he married Mary Brewton Motte, daughter of the celebrated Patriot Rebecca Motte, strengthening his connections among the Lowcountry elite. He developed extensive plantations, became a noted horse breeder, and eventually acquired hundreds of enslaved people, earning the nickname “King Billy” for his wealth and display. He also entered the South Carolina senate. Those later achievements rested upon the land, enslaved economy, kinship, horsemanship, and militia leadership acquired before and during the Revolution. His son Joseph Alston later married Theodosia Burr and became governor of South Carolina.