William Sheridan Allen was born in Evanston, Illinois. He graduated from Loyola Academy in Wilmette, Illinois, and earned a bachelor’s degree in history from the University of Michigan, a master’s in history from the University of Connecticut, and his doctorate in history from the University of Minnesota. He also studied at the Free University of Berlin and the University of Gottingen. In the early 1950s, he went to a small, predominantly Protestant middle-class town in Hanover, Germany, to research its history during the years between World War I and World War II. From this work he produced his first book, The Nazi Seizure of Power: The Experience of a Single German Town, 1922-1945 (1965). He conducted an exhaustive study of the local newspapers and periodicals, town budgets, crime statistics, and court cases, among other sources. With his analysis, he debunked the idea that Hitler and the Nazi regime came to power through violence. Instead, he explained, the Nazis "seized" power through democratic tactics that won localized support by promising Germans to "get their country back to greatness." The book was extremely influential and became a classic work used as a textbook in college German and European history courses. Allen taught at several universities, including the Massachusetts Institute of Technology, University of Missouri and Wayne State University, before joining the history faculty at the University of Buffalo, where he taught for more than 30 years. He served as chairman of the history department and often lectured in area high schools about the Holocaust.