Williamson was born in Scotland. As a youngster he emigrated with his parents, whose names are not known, to British Colonial America and settled in Ninety Six, South Carolina. Williamson grew up to became a prominent businessman in South Carolina. At the start of the War of Independence Williamson built a small fort at Ninety Six. He participated in campaigns against local Loyalist forces and took part in an expedition against the British in Florida. After the fall of Charleston he capitulated to the British and tried to persuade others to follow his lead. His actions were considered traitorous by his former compatriots, who took him prisoner on two occasions – the first time to persuade him to reconsider, and the second time to stand trial. However, after the second abduction, the raiding party led by Colonel Isaac Hayne was intercepted within 24 hours by a British column, who freed Williams and took Hayne prisoner.
After the war Nathanael Greene revealed that Williamson was not the turncoat he appeared to be, as he had been providing intelligence to the Continental Army, but to many of his contemporaries he remained a controversial figure.
^ abThe Oxford Essential Dictionary of the U.S. Military., Oxford University Press, Inc., 2002. "Williamson, Andrew (1730?–1786)", website of www.answers.com, Retrieved 2009-11-03
^ abBenson John Lossing. The pictorial field-book of the revolution: or, Illustrations, by pen and pencil, of the history, biography, scenery, relics, and traditions of the war for independence, Volume 2, Harper & brothers, 1860. Footnote 3, pp.506,507