The building, neo-Classical and in the Ionic order, was completed in 1868, and extended twice since. Some of the extension works were funded by donations from local businessman J. G. Graves. The front part of the building was the city museum, while the rear was the art gallery. The art gallery is a Grade II* listed building.
Weston Park Museum was named the Sheffield City Museum and Mappin Art Gallery until 2006. It opened in 1875, and housed Sheffield's archaeology, natural history, decorative art and social history collections.