A native of Canton, Pennsylvania, he is married to Lana Hartman Landon, a writer and teacher. Their daughter, Nora, is a instructor at Oakwood Friends School in Poughkeepsie, New York. Landon is a graduate of Columbia University and the Disciples Divinity House of the University of Chicago and has written and lectured on issues related to the history and ecclesiology of the Christian Church (Disciples of Christ).

Landon was ordained in 1975 at First Christian Church of Chicago Heights and later served as pastor for congregations in Wisconsin and Indiana for 12 years. He then served eight years as executive director of East Central Colleges, a consortium of independent colleges in Ohio, Pennsylvania and West Virginia, while continuing to serve as an interim minister for nearby congregations. He is currently a member of Compton Heights Christian Church (Disciples of Christ) in St. Louis, Missouri.

During his term as HELM's president, Landon led what had been the Division of Higher Education clarify its mission and focus its energies on leader development. He also served on the Mission Funding Implementation Team, the Mission Funding Task Force, the General Board's Mission Council, and the Standing Committee on Renewal and Structural Reform. He is currently the convener of the Leader Development Working Group and a trustee for the Oreon E. Scott Foundation.

Landon has also served on the town council and as acting municipal judge for the Town of Bethany, West Virginia, and as a director for Wabash Valley Human Services as well as a variety of other community groups.

Dennis is a trivia expert and has contributed to a book of humorous essays on the work of Franz Bibfeldt, the world's most famous non-existent theologian. He spends his spare time reading, collecting different incarnations of the Jack In The Box spokesman on eBay, and enjoying "The Simpsons" and reruns of "Buffy The Vampire Slayer."