Allen is a author, educator, and historian. He has written four books: The Analyst; Teacher of Civil War Generals; Your Affectionate Father, Charles F. Smith; Charles A. Marvin - "One Year. Six Months, and Eleven Days", and Preparing for Disunion. He teaches classes on the American Civil War at Collin College. He has visited more than 130 Civil War sites and shares his over 4,000 photographs on Civil-War-Journeys.org. He blogs about the Civil War on Salient Points.