In 1953, HGA's fifty year collaborative tradition began with the partnership of two young architects, Richard Hammel and Curtis Green, who sought to bring the best of modern design to Minnesota. Formerly employed as an architect for the St. Paul Public Schools, Hammel was a recent graduate of Harvard's Graduate School of Design who was nurturing new ideas in academic programming and design. As a student of Alvar Aalto in the MIT Architecture program, Curt Green was integrating new design ideas from Northern Europe and across the United States in his own work.

HGA's first office was situated in the basement of Green's house - itself a testimony to the optimistic and open modernism of their time. With the addition of the Harvard-educated Bruce Abrahamson to the firm in 1954, the office became a model for innovative design with a team approach to problem solving. With single-loaded corridors and broad windows drawing in daylight, Highland Park Junior High School in Saint Paul was the young firm's first major school commission. HGA soon promoted its modernist ideas to school districts across Minnesota. By the end of the 1950s, Hammel, Green and Abrahamson, Inc. was established as some of the most innovative school designers in the Upper Midwest. After incorporation, the first order of business was to discuss bringing in engineers and in January 1959, the company hired its first mechanical engineer. In hiring engineers, HGA made a prescient decision - to become a full-service firm.