In 2000, Arnn became the 12th president of Hillsdale College, a liberal arts college founded in 1844 that accepts no federal or state taxpayer subsidies for any of its operations. In 2010, Hillsdale opened its Allan P. Kirby, Jr. Center for Constitutional Studies and Citizenship, which is dedicated to teaching the Constitution, the debate that brought it to life, and the principles that give it meaning. It is located across the street from The Heritage Foundation in Washington, D.C.

Arnn studied political science and accounting at Arkansas State University and earned his master’s degree and PhD in government at the Claremont Graduate School. He studied international history at the London School of Economics and modern history at Worcester College at Oxford University and worked as director of research for Sir Martin Gilbert, the official biographer of Winston Churchill. Arnn has studied and taught Churchill without interruption for four decades. In 2012, he assumed responsibility for editing the final six document volumes of the Churchill biography.

In 1985, Arnn became president of the Claremont Institute, a think tank based in southern California. He remained at Claremont until 2000. He is Vice Chairman of the Claremont Institute’s board of directors and a member of the board of directors of the Henry Salvatori Center of Claremont McKenna College. He is also a member of the American Political Science Association, the Mont Pelerin Society, the International Churchill Society, and the Philanthropy Roundtable. He is the author of several books, including Churchill’s Trial (2015), The Founders’ Key (2013), and Liberty and Learning (2004).

Arnn is a 2015 recipient of The Lynde and Harry Bradley Foundation’s Bradley Prize.