Charles Robert (Bob) Harmon was born in Washington State on April 12, 1925, and grew up in Olympia. His parents, Don and Laura Harmon, worked in the shipping industry. He had two brothers, Barry and Neil.

In 1944, at the age of 19, Harmon enlisted in the U.S. Army and served in the 80th Division of Patton’s Third Army. Among other distinctions, Private First Class Harmon fought in the Battle of the Bulge and was present at the liberation of Buchenwald concentration camp in 1945. He also helped to recover priceless artwork from across Europe that had been stolen by the Nazis and hidden in a salt mine in Altaussee, Austria. Harmon's service in the U.S. Army would deeply inspire his later life and work. He returned numerous times to Germany at the invitation of the German government, which honored his contributions to the liberation of Buchenwald.

After the war, Harmon enrolled as a student at Seattle University (then Seattle College) under the GI Bill. It was there that he met his future wife, fellow student Virginia (Gina) Connolly. Harmon graduated from Seattle University with a Bachelor of Social Science degree in 1950, and he and Gina wed in 1951. (Gina would return to complete her Bachelor of Arts degree in 1958, graduating magna cum laude.) Together, Bob and Gina raised four children.

In 1953, Bob Harmon began teaching in the History department at Seattle University. His service to the university would continue for the rest of his life. In 1969, he was named Distinguished Teacher of the Year, the first of many accolades from his students and colleagues. Among his many achievements, he directed the Night School in the 1960s, developed the Honors Program, and taught classes and gave public lectures on American military history. He was named Professor Emeritus upon his retirement in 1993, and continued to teach until 2013.

Harmon and his wife Gina were married for over 70 years, until Harmon's death in 2023.