Trained as a cooper. Moved to Philadelphia (1745), where he went into business as a merchant. Held no elective office (except overseer of the poor, 1753), but was very active in civic and religious organizations, including the Library Company, the Fellowship Fire Company, and the Philadelphia Quaker meeting. Elected to the American Philosophical Society (1768), served on numerous committees, and subscribed to several civic projects. Signed non-importation agreement (1765), but remained neutral in the Revolutionary War. Retired from business during the war and devoted his time to science and philanthropy. Collected subscriptions for the erection of the American Philosophical Society building (c. 1780-85).
Quaker. Son of Thomas and Sarah (Cowgill) Clifford of Bucks County, Pennsylvania. Married Anna Guest (1743); nine children.