"Encyclopedia Dubuque is the online authority for all things Dubuque, written by the people who know the city best.”
Marshall Cohen—researcher and producer, CNN
JAGNOW, David. (Dubuque, IA- ). Jagnow was one of two discoverers of Coldwater Cave believed to be the largest cave ever discovered in Iowa. Water inside the cave remains a constant 47 degrees with the air temperature only a few degrees warmer.
Iowa Underground: A Guide to the State's Subterranean Treasures, p. 86 - Google Books Result books.google.com/books?isbn=1931599394
Oneota Flow: The Upper Iowa River and Its People, p. 74 74 - Google Books Result books.google.com/books?isbn=1587298368