The building originally measured  by , but an extension in 1922 gave it its current dimensions. The unique façade of the Old Slave Mart consists of  octagonal pillars at each end, with a central elliptical arch comprising the entrance.
Originally, the building had a certain size, but an expansion in 1922 increased its size to what it is today. The unique exterior of the Old Slave Mart features eight-sided pillars at both ends and a central oval-shaped entrance.