Hellmuth, Obata and Kassabaum
HOK (formerly Hellmuth, Obata + Kassabaum) is a U.S. based architecture, interiors, engineering, planning, urban design and consulting firm with offices in several other countries. As of 2012, HOK is the largest U.S.-based architecture-engineering firm and the second-largest interior design firm. The firm maintains more than 1,600 professional staff across a global network of 24 offices and is active in all major architectural specialties. Its senior leaders are located in several different locations across the world. Its headquarters are in One Metropolitan Square in St. Louis.
HOK was established in St. Louis, Missouri, in 1955. The firm's name is derived from the surnames of its three founding partners: George Hellmuth, Gyo Obata and George Kassabaum, all graduates of the School of Architecture at Washington University in St. Louis. The new design firm started with 26 employees and the complementary talents of its three founders, who each assumed a distinct role in the firm's operations. Hellmuth focused on design, Obata on design and Kassabaum on project management.
In 1944, George Hellmuth, while director of marketing at Smith, Hinchman and Grylls (SHG), wrote a document on how to expand a successful practice for a large architect-engineer firm. Hellmuth embraced the roadmap for his new firm, Hellmuth, Yamasaki and Leinweber (HY+L) when it was formed in 1949 and later for Hellmuth, Obata & Kassabaum (HOK) when that firm was founded in 1955. Hellmuth's document, referred to as his master plan for a large firm, included thoughts on the importance of obtaining business from large clients who have work to perform in several parts of the world as well as the benefit of developing specialty areas of design practice. Hellmuth's recommended marketing procedures helped to shape HOK as it grew and are in still in use today.
The practice's first building designs were schools in St. Louis suburbs, and St. Thomas Aquinas High School in Florissant was the first private/parochial school designed by the firm. Another prominent school they designed was the Saint Louis Priory School. By the mid-1960s, the firm was winning commissions across the United States and began to open additional offices, starting with San Francisco in 1966 for the design of a library at Stanford University and Dallas in 1968 for the master planning and design of Dallas-Fort Worth International Airport. Also in 1968, HOK launched its interior design practice. HOK also expanded into Washington, DC, after winning the commission to design the Smithsonian National Air and Space Museum. In 1973, HOK established a presence in New York by acquiring Kahn & Jacobs, designers of many New York City skyscrapers. By the 1970s, the firm was operating internationally and in 1975 the firm was named as architect of the $3.5 billion King Saud University in Riyadh, at the time the single largest building project in the world.
In 1983, HOK formed HOK Sport Venue Event, which became a leader in designing sport stadiums, arenas and convention centers. In January 2009, the Board of HOK Group, Inc. and managers of HOK Sports Facilities, LLC transferred ownership of HOK Sport to leaders of that practice. The company has since fully separated itself from HOK, and is now known as Populous. Populous continues to be the leader in the design of sport and exhibition venues across the world, including some of the more famous new venues we see today.
HOK's first office outside the United States opened in Hong Kong in 1984. In 1987, the firm opened a London office and then, in 1995, expanded this London practice by merging with renowned UK architectural practice Cecil Denny Highton. In November 1994, HOK acquired CRSS Architects, Inc. based in Houston, Texas, adding offices in Houston and Atlanta. HOK established its first offices in Canada (Toronto and Ottawa) in 1997 with the acquisition of Urbana Architects.
By 2007, international work represented more than 40% of HOK's annual revenue. In 2008, HOK opened an office in Mumbai, India. In 2010, it established offices in Seattle, Washington, and Ho Chi Minh City, Vietnam.
In 2012, HOK Chairman Bill Valentine retired after 50 years with the firm. HOK Chief Executive Officer Patrick MacLeamy, FAIA, assumed the role of chairman.
Architects at the firm include Yann Weymouth.
Innovation and sustainable design 
HOK is an innovator in the building design industry and has greatly influenced the business of architecture. In 1983 HOK introduced HOK Draw, one of the first computer-aided drafting software products that specialized in conceptual architectural design. More recently, HOK has made a commitment to using Building Information Modeling (BIM) to streamline the design and construction process. In 2012, Building Design + Construction ranked HOK the No. 1 BIM Architecture Firm.
HOK is a leader in sustainable design. Professionals in the firm authored one of the industry's most respected resources on the topic, "The HOK Guidebook to Sustainable Design," originally published in 2000 by John Wiley & Sons. A second edition of the book was published in 2005. In September 2008, to better integrate nature's innovations into the design of buildings, communities and cities worldwide, HOK announced an alliance with the Biomimicry Group, co-founded by Janine Benyus. In 2010, HOK and energy and daylighting consultant The Weidt Group completed design of Net Zero Court, a 170,735-square-foot, market-rate, zero-emissions class A commercial office building in St. Louis.
In 2012, DesignIntelligence magazine ranked HOK the "No. 1 Role Model for Sustainable and High-Performance Design". HOK currently has more than 900 LEED (Leadership in Energy and Environmental Design) credentialed professionals and 145 LEED certified projects.
Global offices 
- Los Angeles
- New York
- St. Louis
- San Francisco
- Washington, DC
- Hong Kong
- HOK Euronet - affiliated firms in Amsterdam, Brussels, Madrid, Milan, Paris and Rome
Selected projects 
- 1962: The Priory Chapel, St. Louis, Missouri, United States
- 1970: Houston Galleria, Houston, Texas, United States
- 1970: Xerox PARC, Palo Alto, California, United States
- 1975: King Saud University, Riyadh, Saudi Arabia
- 1976: National Air and Space Museum, Washington, D.C., United States
- 1979: Cecil H. Green Library, Stanford University, Palo Alto, California, United States
- 1981: Moscone Center, San Francisco, California, United States
- 1981: Metropolitan Square, St. Louis, Missouri, United States – Current location of HOK St. Louis office
- 1982: Levi's Plaza, San Francisco, California, United States
- 1983: King Khaled International Airport, Riyadh, Saudi Arabia
- 1985: St. Louis Union Station Renovation and Redevelopment, St. Louis, Missouri, United States
- 1986: BP Building Cleveland, Ohio, United States
- 1986: Kellogg Company Headquarters Battle Creek, Michigan, United States
- 1986: Riverchase Galleria Birmingham, Alabama, United States
- 1991: 801 Grand, Des Moines, Iowa, United States (tallest building in Iowa)
- 1992: Oriole Park at Camden Yards, Baltimore, Maryland, United States
- 1992: Schapiro Center for Engineering and Physical Science Research (CEPSR), Columbia University, New York, New York, United States
- 1993: Apple Inc. R&D Campus, Cupertino, California, United States
- 1994: Independence Temple, Independence, Missouri, United States
- 1995: Tokyo Telecom Center, Tokyo, Japan (co-designers)
- 1996: Tuntex Sky Tower, Kaohsiung, Taiwan (Republic of China)
- 1996-1997: Nortel Brampton Centre HQ, Brampton, Ontario, Canada
- 1997: Foreign and Commonwealth Office Restoration, London, England
- 1997: George Bush Presidential Library, College Station, Texas, United States (on the campus of Texas A&M University)
- 1999: Northwestern Memorial Hospital Facility Replacement and Redevelopment, Chicago, Illinois, United States (co-designers)
- 1999: Edificio Malecon Office Tower, Buenos Aires, Argentina
- 1999: Boeing Leadership Center, St. Louis, Missouri
- 2000: Passenger Terminal Amsterdam, Amsterdam, The Netherlands
- 2001: United States Environmental Protection Agency Research Center, Research Triangle Park, North Carolina, United States (1.2 million-sq.-ft. campus)
- 2002: Darwin Centre at the Natural History Museum, Passenger Terminal Cork, Cork Airport, Ireland
- 2002: Alfred A. Arraj U.S. Courthouse, Denver, Colorado, United States
- 2003: Steven F. Udvar-Hazy Center of the National Air and Space Museum, Chantilly, Virginia, United States
- 2004: Harlem Hospital Center Master Plan and Patient Pavilion, New York, New York, United States
- 2005: Cisco Systems Executive Briefing Center Interior Design, San Jose, California, United States
- 2005: Terminal A at Logan International Airport, Boston, Massachusetts, United States (world's first LEED certified air terminal building)
- 2006: Lavasa Hill Station Master Plan and Design Guidelines, Moss Valley, Pune, India
- 2006: Natural History Museum of the Adirondacks (The Wild Center), Tupper Lake, New York, United States
- 2006: SJ Berwin European Headquarters Interior Design, London, England, (Business Week/Architectural Record Award winner)
- 2007: Dubai Marina, Dubai, United Arab Emirates
- 2008: Frost Art Museum, Florida International University, Miami, Florida, United States
- 2008: Midfield Terminal at the Indianapolis International Airport, Indianapolis, Indiana, United States (master designer)
- 2009: Doha City Centre, Doha, Qatar, (design of five hotel towers for largest retail development in the Middle East)
- 2009: King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia (Saudi Arabia's first LEED certified project and the world's largest LEED Platinum project)
- 2009: Carnival House, head office of Carnival UK, Southampton, England
- 2009: Bakrie Tower, Jakarta, Indonesia
- 2010: Indira Gandhi International Airport – Terminal 3, Delhi, India (LEED Gold certification)
- 2010: New Building 20 at NASA's Lyndon B. Johnson Space Center, Houston, Texas, (LEED Platinum certification)
- 2011: Salvador Dalí Museum, St. Petersburg, Florida
- 2011: Brigade Gateway Enclave, Bengaluru, India
- 2012: Canon USA Headquarters, Melville, New York
- 2012: Baku Flame Towers, Baku, Azerbaijan
- 2012: Harlem Hospital Center Mural Pavilion, New York City
- 2013: Hamad International Airport Passenger Terminal Complex, Doha, Qatar
- 2013: Porsche U.S. Headquarters and Customer Experience Center, Atlanta, Georgia
- 2013: San Francisco Mint Adaptive Reuse, San Francisco, California
- 2013: Abu Dhabi National Oil Company Headquarters, Abu Dhabi, United Arab Emirates
- 2014: Capital Market Authority Tower, Riyadh, Saudi Arabia
- 2016: University at Buffalo School of Medicine and Biomedical Sciences, Buffalo, New York
- 2016: Ri.MED Biomedical Research and Biotechnology Center, Palermo, Italy
- "Top 500 Design Firms 2012', "Engineering News-Record", April 20, 2012
- "2012 Interior Design Giants', "Interior Design", January 1, 2012.
- Dietsch, Deborah K. (November 17, 2008). "HOK's Bill Hellmuth: On top of the world".
- "Uncertain Economy Pushes Design Firms To Diversify Their Portfolios," Engineering News-Record", June 23, 2008.
- "BIM at HOK', "AEC Magazine", January 30, 2007.
- "BIM Finally Starting to Pay Off for AEC Firms', "Building Design + Construction", July 19, 2012.
- "HOK Earns Sustainable Leadership Award', "Interior Design", May 9, 2006.
- "HOK and Biomimicry Guild Forge Alliance for Bio-Inspired Design Excellence', "Treehugger.com", September 22, 2008.
- " New Zero: Two global design firms issue a call to action and lead by example, "Contract", October 2010.
- "Professionals of Agility and Responsibility, "DesignIntelligence", July 9, 2012.