It is a two-story masonry building, capped by a hipped roof with cupola and set on a high brick basement.
The main facade faces west, and has a projecting three-bay gabled section at its center with entrances recessed in three round-arch openings on the first floor, and sash windows set in bays articulated by Ionic pilasters on the second.
During the American Revolution, confiscated tea was stored here in 1774, and it is where South Carolina's revolutionary leadership councils were held.
[4] The building housed the South Carolina convention to ratify the United States Constitution in 1788, and was the site of many of the events in George Washington's week-long stay in Charleston.
According to Frederic Bancroft in Slave-Trading in the Old South, "From colonial days until after the middle of the nineteenth century from several hundred to many thousand slaves were annually sold to the highest bidders, in front or just north of this building.
As the postoffice was long in the Exchange, visitors as well as residents called there daily for their mail, and, after about 10 A. M. on sale-days, were sure to notice the crowd that gathered about the slaves.