Denver native Mark A. Barnhouse has published four history books on Denver and leads the popular "Historic Sixteenth Street" walking tour for the annual Doors Open Denver celebration. He earned his BA in history and English literature from the University of Colorado at Denver and has continued to research and write. Fascinated by the ways his city has changed over time, Mark is particularly interested in the histories of old, vanished department stores, having spent many hours in them as a youth.