William Thomson was born in Pennsylvania on January 16, 1727. A resident of Orangeburgh District, South Carolina, he was a local sheriff and a colonel in the militia in 1775. In June 1775 he became a lt. col. in the 3rd Regiment of the South Carolina State Troops. He was promoted to full colonel in 1776 and led troops during the Battle of Fort Moultrie. He was captured and paroled during the fall of Charleston in 1780. He died in Virginia on November 22, 1796.