Williams guest lectured at more than fifty colleges in the United States and Europe. He participated in countless Civil War Roundtables. In 1964, he received the Harry S. Truman Award in Civil War History. During his career, Williams was honored with Doctor of Law recognition from Northland College (1953); a Guggenheim Fellow (1957); Doctor of Letters from Bradley University in Peoria, Illinois (1959); Harmsworth Professor of American History, Queen's College, Oxford, England (1966–1967), and Doctor of Humane Letters from Loyola University and Tulane University, both in New Orleans, in 1974 and 1979, respectively.