Born in Hackensack, New Jersey, Cassedy attended the common schools. He studied law. He was admitted to the bar in 1809 and commenced practice in Hackensack. Postmaster of Hackensack from June 10, 1805, to January 1, 1806.
Cassedy was elected as a Democratic-Republican to the Seventeenth Congress, reelected as a Jacksonian Democratic-Republican to the Eighteenth Congress, and reelected as a Jacksonian to the Nineteenth Congress (March 4, 1821 – March 3, 1827). He died in Hackensack, December 31, 1842, and was interred there in the First Reformed Dutch Church Cemetery.
- George Cassedy, Biographical Directory of the United States Congress. Accessed August 22, 2007.