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The Johnson Building
Central Library
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Exterior of Johnson Building
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The Great Hall
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On December 11, 1972, an addition to Central Library in Copley Square opened. The building was designed by noted architect Philip Johnson, with collaboration from the Architects Design Group of Boston, who observed two requests: to observe the existing roof line of the McKim Building, and to use material (Milford granite) that would harmonize with the exterior of the existing Central Library building.

The Central Library's McKim and Johnson buildings, as they are now known, are linked on three levels for easy access to all the resources of the library. Deferrari Hall, the main stairways, and lobby have granite flooring and walls, to match the exterior of the building. The Johnson Building occupies ten levels, four levels of public services, one of behind-the-scenes library processing and administration, four levels of book stacks for the research collection, and one level shared by utilities, maintenance and stacks.

In order to contain nine floors and the mezzanine level within the height limitation respecting the existing building, unique structural and mechanical systems were developed. The upper five floors are suspended from huge roof trusses which form the mechanical penthouse. This allows for the maximum amount of usable space and eliminated the need for a forest of columns on the second floor. The Johnson Building contains approximately 1,900 tons of reinforcing steel rods and 2,100 tons of structural steel — enough to make a 5-inch diameter pipe reaching from the Earth to a 100-mile-high orbiting space craft. The 25,000 cubic yards of concrete used for the building could create a sidewalk back from the space craft to Earth.