George Hellmuth, Gyo Obata, George Kassabaum. HOK

HOK is a global architecture, engineering, planning and design studio. Founded in 1955 in St. Louis, Missouri, USA by architects George F. Hellmuth (1907–1999), Gyo Obata (1923–2022), and George E. Kassabaum (1920–1988), the firm’s 1,700 people collaborate across a network of 27 offices on three continents.

Celebrating our 70th anniversary in 2025, HOK is a collective of future-forward thinkers and designers who are driven to face the critical challenges of our time. We are dedicated to improving people’s lives, serving our clients and healing the planet. Together, we cultivate a culture of design excellence at the confluence of art and science, blending the power of creative expression with a clear sense of purpose.

HOK has been carbon neutral since 2022 and is dedicated to achieving net-zero emissions in the projects we design by 2030. In 2024, on average, HOK’s projects surpassed the American Institute of Architects (AIA) 2030 energy reduction targets, achieving a 68% reduction in energy use intensity compared to baseline levels, with many already meeting or exceeding the targets. We’re committed to addressing both operational and embodied carbon through innovative research and design strategies, including structural optimization and sustainable material selection.