In 1975, William began a career in architecture by enrolling in the Boston Architectural Center. His education at the BAC was supplemented with classes at Harvard Graduate School of Design, Massachusetts Institute of Technology, and the Rome Academy in Italy. He opened William Hall Architects in 1991 after spending 10 years at The Architects Collaborative and several years practicing in Rome, Italy and Boston. He operates a small real-estate development company as well as his firm. His design philosophy embraces "less is more," and William Hall Architects embraced efficiency in use of materials and energy decades before it became popular.