While working for Minoru Yamasaki in the early 1950s, George Hellmuth and Gyo Obata collaborated on St. Louis’ Lambert International Airport. In 1955 the two partnered with George Kassabaum, establishing the St. Louis-based firm, Hellmuth, Obata + Kassabaum, Inc. (now known as HOK). All three partners had graduated from the Washington University School of Architecture (now College of Architecture – Sam Fox School of Design & Visual Arts) and played different roles in the nascent firm: Hellmuth handling operations, Obata, design, and Kassabaum, marketing. With a staff of 26 employees, the firm initially made their reputation in the St. Louis region with several school and higher education projects, including Bristol Elementary in Webster Groves, Missouri (1956) and the Southern Illinois University campus in Edwardsville, Illinois (1961). In the 1960s the firm became known for their Modernist projects, including Obata’s circular, modernist Abbey Church in Creve Coeur, Missouri (1962) and the St. Louis Science Center Space Science Building (1963), situated in Forest Park. Notable work outside the St. Louis area includes the corporate headquarters for IBM Labs in Los Gatos, California (1964), the Dallas-Ft. Worth International Airport (1972), and the National Air and Space Museum in Washington, D.C. (1976), which opened as part of the nation’s bicentennial celebration.
In the late 1960s and early 1970s, the firm grew and expanded, merging with New York City-based Kahn & Jacobs, P.C., and opening offices in San Francisco, Dallas, and Washington, D.C. The firm designed facilities for the 1980 Winter Olympics in Lake Placid, NY, and subsequently opened HOK Sport, a subsidiary devoted to sport and venue design. After the retirement of George Hellmuth (1979) and the death of George Kassabaum (1982), new leadership transformed the firm into a global practice, opening an office in Hong Kong in 1984. The firm now is now the largest U.S.-based architecture and engineering practice maintaining offices throughout North America, Europe, and Asia.