In 2001, David E. Zitarelli of Temple University published EPADEL: A Semisesquicentennial History, 1926-2000. It's a wonderful history of the organization's inception, development, and the people that made it possible.
The version linked above was created by Bud Boman (Penn State Harrisburg), based on the original source PDF for David Zitarelli's book.
A project to update Zitarelli's history for the past two decades is underway by Doug Ensley. If you have anything you'd like to contribute, please contact him at dougensley@gmail.com.