Gregory is Chairman of the Theodore Roosevelt Association which he joined in 1984. He is a native of Carlisle, Pennsylvania. He served for 24 years as an officer in the U.S. Marine Corps. He earned a BA in History from Millersville University of Pennsylvania, a Master of Military Studies from the U.S. Marine Corps Command & Staff College, and an MA in Museum Studies from Johns Hopkins University. He is a Theodore Roosevelt scholar and a collector of Roosevelt material focused on TR’s writing. He resides in Maryland and is a writer and advisor to the Commander of U.S. Cyber Command.