Abstract: Documents of Professor Clifford H. Mortimer (1911-2010) include correspondence, slides, images, and research from one of the premier limnologists in the field. The primary notes in the collection contain research charts and data, vessel logs, slides and notes related to Mortimer's work on Lake Windermere in England in the 1950s and across the Great Lakes in the U.S. throughout the 1960s to the 1980s, especially regarding his time at UW-Milwaukee as the first Director of the Center for Great Lakes Studies (now the School of Freshwater Sciences).