William Magear "Boss" Tweed (April 3, 1823 – April 12, 1878) was an American politician most notable for being the political boss of Tammany Hall, the Democratic Party's 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 Railroad, a director of the Tenth National Bank, a director of the New-York Printing Company, the proprietor of the Metropolitan Hotel, a significant stockholder in iron mines and gas companies, a board member of the Harlem Gas Light Company, a board member of the Third Avenue Railway Company, a board member of the Brooklyn Bridge Company, and the president of the Guardian Savings Bank.