Through his marriage, numerous land grants, and purchases, Brewton accumulated a large quantity of real estate. However, he made his fortune principally as a merchant rather than as a planter, becoming one of the wealthiest men in South Carolina. Brewton served in the Commons House of Assembly from 1765 until his death, representing the parishes of St. Philip’s, St. John’s Colleton, and St. Michael’s in succession. In 1773 Lieutenant Governor William Bull recommended him for a seat on the Royal Council, but Brewton’s support of antigovernment measures led him to decline the seat. In July 1774 Brewton stood as a conservative South Carolina candidate for the First Continental Congress, but he lost to the more radical Christopher Gadsden.