William M. Tweed (April 3, 1823 - April 12, 1878), sometimes informally called Boss Tweed, was an American politician who was convicted for stealing between 40 million and 200 million dollars from New York City taxpayers through political corruption. Tweed was head of Tammany Hall, the Democratic Party political machine that played a major role in the politics of 19th century New York. He died in jail.