Robert Alonzo Ritterbush was born October 13, 1891, in
Oakes, North Dakota, to William Donald Ritterbush, a contractor, and Elizabeth (Dyer) Ritterbush. He was educated at the
Ohio Mechanics Institute, later part of the
University of Cincinnati, graduating in 1917. During
World War I he served with the navy in France. In 1920 he returned to North Dakota, settling in
Bismarck, where he and his brother, Clarence W. Ritterbush (1893–1990), formed a partnership with established architect
Arthur Van Horn. When Van Horn died in 1931 the brothers succeeded to the practice, which they renamed Ritterbush Brothers. The elder Ritterbush retired as partner in 1967, but was retained as a consultant until 1973, when he fully retired. In 1922 Ritterbush joined the North Dakota Association of Architects, of which Van Horn had been a founding member in 1917. In 1953 the association achieved its long-time goal of affiliating with the
American Institute of Architects, and all of its members, including Ritterbush, became members of the AIA. From the time he joined in 1922 until 1965 he was secretary–treasurer of the North Dakota association. In 1966, following his retirement from that office, the association honored him for his "46 years of practice in architecture and outstanding service to the profession." In 1969 he was elected a
Fellow of the American Institute of Architects, the organization's highest membership honor. ==Personal life==