Sarah Fairfax was born on December 31, 1730, in Salem, Massachusetts, the daughter of William Fairfax and Deborah Clarke Fairfax. Her father was a British colonial official and member of the extended Fairfax family; her mother came from a Salem mercantile household. Sarah’s childhood was unusually mobile, reflecting her father’s customs and land-management appointments. The family lived in Massachusetts before moving to Virginia, where William became agent for Lord Fairfax’s Northern Neck proprietary. Sarah grew up at Belvoir plantation on the Potomac among step-siblings and full siblings in a large blended household. She received the private education of a gentry daughter: reading, writing, religion, needlework, music, household accounts, and social etiquette. At Belvoir, Sarah encountered visiting planters, merchants, officers, and relatives. The household’s comfort depended upon enslaved labor. Her position made marriage both a personal and economic alliance. In 1749 she married John Carlyle, a Scottish-born Alexandria merchant whose commercial success was transforming him into a Virginia gentleman. Sarah became mistress of the Carlyle household and bore several children, but her adult life was brief. Childbirth and disease posed serious risks even to wealthy women. She died in 1761, leaving Carlyle a widower and surviving children without their mother. Before her marriage connected the Fairfaxes to Alexandria’s merchant elite, Sarah had been shaped by New England birth, colonial migration, a blended official family, Belvoir’s plantation culture, private female education, and expectations of hospitality and household management. Her life illustrates how daughters helped convert imperial office and aristocratic connection into local commercial alliances. The scarcity of her personal writings makes her domestic work less visible than the careers of the men around her, but it was central to family advancement.