William Magear Tweed – sometimes erroneously referred to as William Marcy Tweed (see below), and widely known as "Boss" Tweed – was an American politician most notable for being the "boss" of Tammany Hall, the Democratic Party political machine that played a major role in the politics of 19th century New York City and State. At the height of his influence, Tweed was the third-largest landowner in New York City, a director of the Erie Railway, the Tenth National Bank, and the New-York Printing Company, as well as proprietor of the Metropolitan Hotel.

Tweed was elected to the United States House of Representatives in 1852, and the New York County Board of Supervisors in 1858, the year he became the "Grand Sachem" of Tammany Hall. He was also elected to the New York State Senate in 1867, but Tweed's greatest influence came from being an appointed member of a number of boards and commissions, his control over political patronage in New York City through Tammany, and his ability to ensure the loyalty of voters through jobs he could create and dispense on city-related projects.

Tweed was convicted for stealing an amount estimated by an aldermen's committee in 1877 at between $25 million and $45 million from New York City taxpayers through political corruption, although later estimates ranged as high as $200 million. He died in the Ludlow Street Jail.

Tweed never signed his name with anything other than a plain "M.", and his middle name is often mistakenly listed, even by otherwise reputable sources, as "Marcy", rather than "Magear", but Tweed's son's name was William Magear Tweed, Jr. The confusion is almost certainly because of a Thomas Nast cartoon with a picture of Tweed, supplemented with a quote from William L. Marcy, the former governor of New York.

http://en.wikipedia.org/wiki/William_M._Tweed