This chamber originally housed the Court of Sessions (a Criminal Court) and the Superior Court. As the largest room in the building, the court room was occasionally used for large celebrations and meetings during the first half of the 19th century. An 1845 report from a meeting of the Young Women's Industry Association describes the room as "superbly decorated," noting that the drapery behind the baldachin was "of dark crimson and bright gold stars," and the alcove ceiling was "decorated with gold rays and clouds in a dark blue background."
The Board of Aldermen (renamed the City Council in 1938) used the room from 1875 until 1898, when it moved into the newly created Aldermanic Chamber (now the City Council Chamber) on the east side of the building. The room subsequently housed the Municipal Council of 29 and the Board of Estimate and Apportionment, which underwent several transformations, ultimately becoming the Board of Estimate. Consisting of the Mayor, Comptroller, President of the City Council, and Presidents of each of the five boroughs, the Board of Estimate had a wide range of powers, including approval of the City's expense and capital budgets.
In 1912-1913, the room was renovated by architect Grosvenor Atterbury. He installed a cork floor, replastered the ceiling, repainted the room ivory, and added a deep red canopy and wall hangings behind the Mayor's chair. Atterbury also installed long wooden benches that referenced the chamber's past as a court room. These benches currently line the hallways throughout City Hall.
In 1990, the Board of Estimate was abolished, and the chamber was used for public hearings and ceremonies. In 2002, Mayor Michael R. Bloomberg turned the chamber into an open-plan work space known as the Bullpen, where he worked surrounded by his staff.
In 2008, much-needed repairs were made, including the reinforcement of cracked wooden trusses supporting the roof, the upgrade of life-safety systems, and the installation of additional lighting.