 Clagett was born in Portsmouth, New Hampshire, the son of Wyseman Clagett and Lettice (Mitchell) Clagettt.He was admitted to the bar and commenced practice in Litchfield, New Hampshire in 1787.Elected as a Federalist candidate to the Eighth Congress, Clagett served as a United States Representative for the state of New Hampshire from March 4, 1803 – March 3, 1805.