Tammany Hall was a building in New York which was headquarters of the St. Tammany Society. Most Americans use the term Tammany Hall to refer to the New York political organization which became notoriously corrupt under the leadership of William M. (Boss) Tweed.
Although it is commonly held to have been an example of political corruption, Tammany Hall had a very long history in U.S. Politics, and was a very important champion of populism, anti-elitism, anti-Federalism, and the development of the Democratic Party.
Tammany Hall was a very inclusive organization, and worked from early in it's history to procure voting rights for ordinary citizens. Tammany Hall under the influence of Aaron Burr developed schemes such as communal ownership to allow working class males to buy a low-cost share in real estate, thereby becoming "property owners" and eligible to vote in New York and Federal elections, and the Manhattan Company, an early counter to monopoly banking interests which allowed common men to become shareholders. Tammany Hall's campaign was instrumental in the eventual removal of the "property ownership" requirement for electoral franchise, and gaining direct election of US Senators. Obviously, these policies created animosity with the wealthy elites who had controlled the political process, and earned Tammany Hall the eternal enmity of the wealthy, landed, financial, and business elites and aristocrats who would eventually form the traditional core of the Republican Party.
Tammany Hall's reputation also suffered from it's early association with former Vice-President Aaron Burr, who killed former Secretary of the Treasury, Founding Father, New York financier, Alexander Hamilton in a duel.
Tammany Hall lost much of it's power and prestige, when New York politics was cleaned up by Mayor LaGuardia and FDR.