projects. The firm of Skidmore, Owings & Merrill was founded in Chicago in 1936 by Louis Skidmore and Nathaniel Owings, and joined in 1939 by engineer John Merrill, It soon went under the name of SOM. Its first big project was Oak Ridge National Laboratory in Oak Ridge, Tennessee, the gigantic government installation that produced plutonium for the first nuclear weapons. In 1964 the firm had eighteen "partner-owners", 54 "associate participants, "and 750 architects, technicians, designers, decorators, and landscape architects. Their style was largely inspired by the work of Ludwig Mies van der Rohe, and their buildings soon had a large place in the New York skyline, including the Manhattan House (1950-51), Lever House (1951–52) and the Manufacturers Trust Company Building (1954). Later buildings by the firm include Beinecke Library at Yale University (1963), the Willis Tower, formerly Sears Tower in Chicago (1973) and One World Trade Center in New York City (2013), which replaced the building destroyed in the terrorist attack of 11 September 2001. Wallace Harrison played a major part in the modern architectural history of New York; as the architectural advisor of the Rockefeller Family, he helped design Rockefeller Center, the major Art Deco architectural project of the 1930s. He was supervising architect for the 1939 New York World's Fair, and, with his partner Max Abramowitz, was the builder and chief architect of the headquarters of the United Nations; Harrison headed a committee of international architects, which included Oscar Niemeyer (who produced the original plan approved by the committee) and Le Corbusier. Other landmark New York buildings designed by Harrison and his firm included Metropolitan Opera House, the master plan for Lincoln Center, and John F. Kennedy International Airport. Philip Johnson Philip Johnson (1906–2005) was one of the youngest and last major figures in American modern architecture. He trained at Harvard with Walter Gropius, then was director of the department of architecture and modern design at the Metropolitan Museum of Art from 1946 to 1954. In 1947, he published a book about Ludwig Mies van der Rohe, and in 1953 designed his own residence, the Glass House in New Canaan, Connecticut in a style modeled after Mies's Farnsworth House. Beginning in 1955 he began to go in his own direction, moving gradually toward expressionism with designs that increasingly departed from the orthodoxies of modern architecture. His final and decisive break with modern architecture was the AT&T Building