Tweed, William Marcy (1823-1878), was an American politician who swindled New York City out of millions of dollars. Tweed, known as "Boss" Tweed, entered politics at an early age. By the 1860's, Tweed became head of Tammany Hall, a powerful group of Democratic politicians. He organized his associates into the Tweed Ring, which sponsored schemes for city improvements. Millions of dollars went into the pockets of Tweed Ring members.