Following the War, Don completed his doctorate and in 1952, left his position at New York University, Albany to join the history department at Chico State. In 1972, he was selected as the CSU Trustees' Outstanding Professor. Until his retirement in 1981, he taught American history and he was a vigorous chair of his department through contentious times. A sought-after public speaker on many subjects, he became an early opponent of the Vietnam War, which he believed, by contrast to World War II, did not meet the standard of necessity. He spoke widely against the new war in his unsuccessful campaign for Congress. In 1999, after Flo's death ended 56 years of marriage, Don married his former colleague, Michele Shover. Don and Flo's children are Michael Lillibridge, Linda Lillibridge (Craig Bishop), Jennifer Lillibridge and Catherine Lillibridge (David York). His grandchildren are Jason (Wendy) Yakich, Julie (Michael) Sawley, Rose (Chris) Conley, Marijeanne (Adam) Birchard, and Nichole (Ella) Lillibridge. Grandchildren in Florida are Jill (John) Heilman, Matthew (Lisa) Lillibridge and Tyler (Nancy) Lillibridge. He leaves 17 great-grandchildren.