William Byrd II briefly sat in Virginia's House of Burgesses in 1696 before returning to England, where he represented colonial interests. He returned to Virginia in 1705 to manage his inheritance, including Westover and extensive landholdings. Enslaved labor sustained his plantation income and household. Appointed to the governor's Council in 1709, he remained associated with it for the rest of his life, though long absences and political disputes interrupted his attendance.

Byrd spent much of 1715–1726 in London. He opposed Lieutenant Governor Alexander Spotswood's policies, sought influence at court, and served as an agent for the House of Burgesses. Back in Virginia, he helped lead the 1728 commission surveying the boundary with North Carolina. He turned the journey into two narratives: a formal History of the Dividing Line and a satirical Secret History that gave fellow travelers invented names. Other accounts described his journeys to western lands and iron mines.

Byrd proposed a town at the falls of the James in 1733; surveyor William Mayo laid out Richmond on his property in 1737. He became the senior councillor in 1743 and died at Westover the next year. His large library and private diaries preserve his reading, business, social visits, sexual conduct, and treatment of enslaved people. Most of his literary work remained unpublished during his lifetime. These writings record both the intellectual pursuits and the coercive authority of a wealthy colonial planter.