 As designed by Charles Bulfinch in 1817 and built over the next five years by Alexander Parris, the building had smaller wings (roughly half the present size), and had a capacity of 73 beds.The stonework for its construction was largely done by the inmates at the Charlestown Prison.The building's capacity was nearly doubled in 1844-46 by the addition of five bays to each of the wings, and the original entrance hall designed by Bulfinch was extensively altered.