In 2003, Clark transformed the historic 64,000 square-foot Carnegie Library building into the City Museum, the only museum dedicated to telling the story of the District of Columbia.
To accomodate the museum, the landmark Carnegie Library building underwent a complete renovation. The Beaux Arts inspired building is a three-story symmetrical structure with 14,000 square feet of exhibit space.
Public spaces are located on the three main levels with the mezzanines used for administrative offices and library and collections storage. The museum also featured an education center with meeting space and a visitor information center. A research library and meeting room open to the public will store the Historical Society of Washington, D.C.'s collections of archives and manuscripts, photographs, publications, prints and maps.