1745–1829, American political leader and Revolutionary War army officer, b. Salem, Mass. He was admitted to the bar (1768) and played an active part in pre-Revolutionary activities against the British. In 1774 and 1775 he was connected with the Massachusetts committee of correspondence. A colonel in the Massachusetts militia, he joined George Washington's army in the American Revolution, served (1777) as Washington's adjutant-general, was a member of the board of war, and was (1780–85) quartermaster general. After the Revolution, he moved to Pennsylvania and was sent by the Pennsylvania government to the Wyoming valley region of Pennsylvania to organize the newly formed Luzerne co. and to represent the state in the dispute over land claims between Connecticut settlers and Pennsylvania. He was a member of the state constitutional convention (1789–90) and negotiated treaties with various Native American tribes for the federal government. He was Postmaster General (1791–95), Secretary of War (1795), and Secretary of State (1795–1800). Pickering was dismissed after President John Adams learned that he had been scheming with the Alexander Hamilton branch of the Federalist party to steer the United States into war with France. Returning to Massachusetts, he became chief justice of the court of common pleas and was later a U.S. Senator (1803–11) and Representative (1813–17). A strong Federalist and an opponent of Adams, Pickering was a leading figure in the Essex Junto and an outspoken opponent of the War of 1812. He wrote Political Essays (1812).
- See biography by his son, O. Pickering, and C. W. Upham (4 vol., 1867–73);.
- Timothy Pickering and American Diplomacy, 1795–1800 (1969). ,