This two-storey, Ontario Georgian style building was constructed in two phases; erected from1848 to1849 and designed after the town hall in Perugia, Italy, the first phase accommodated the offices of town council, a town market and a fire/police station.
It was conceived as something of a stage set: only facades visible on James and King Streets are of channelled Queenston ashlars, while the west and north walls are constructed with a course rubble limestone and brick, respectively. The front facade is surmounted by a tower with a three-faced striking clock and is topped by an octagonal cupola.
The clock is believed to be imported from Europe and continues to chime with the assistance of the original weights which extend from the clock tower to the first floor. The entrance to the building, like that in Perugia, is carved in stone and features upright balustrades which conform to the slope of the stairway. The supporting columns under the copings on each side are individually carved to fit its specific location.
The interior still has handsomely-detailed, glazed panelled-wood doors and various plaster cornices are still intact. The upper floor, originally the Council Chamber and meeting hall, contains 22-foot high ceilings. The first floor, formerly an indoor market, contains 13-foot high ceilings. A semi-deteriorated carved bull's head and a sheaf of wheat on the James Street entrance are all that remain to indicate the use of the east wing basement as a market. The second phase, a northeast wing cut-stone addition to the original structure, was constructed in 1865 to accommodate the relocated County offices and courthouse.
The Old Courthouse is currently home of the Sullivan Mahoney Courthouse Theatre. The building contains the administration and production offices of Carousel Players, the Niagara Symphony Orchestra, the Essential Collective Theatre, a rehearsal studio and a 125-seat performance space. The facility is actively used by local theatre, dance and music organizations from the Niagara region; many are members of the Downtown Alliance for the Performing Arts.