The Martin Luther King Jr. Memorial Library (MLKML) is the central facility of the District of Columbia Public Library (DCPL). Ludwig Mies van der Rohe designed the 400,000 square foot (37,000 m²) steel, brick, and glass structure, and it is a rare example of modern architecture in Washington, D.C. On June 28, 2007 the District of Columbia’s Historic Preservation Review Board designated this building a historic landmark. The designation, which applies to the exterior as well as interior spaces, seeks to preserve Mies' original design while allowing the library necessary flexibility to operate as a contemporary library facility. It was listed on the National Register of Historic Places in 2007. Prior to 1972, Washington's central library was a 1903 Andrew Carnegie-funded building located in Mount Vernon Square. That building was used by the University of the District of Columbia, and is currently occupied by the Historical Society of Washington, D.C.