The material in this collection represents Mueller's work from his first years as a pastor in the Evangelical Association to his retirement from the Episcopacy of the United Methodist Church (1921-1975). The earliest manuscripts include sermons and addresses (1921-1975). The rest of the collection consists of correspondence (1941-1973), photographs (1962-1976), addresses (1921-1975), articles, and clippings (1921-1975). The most sustained record of Mueller's work begins in the 1940's with Mueller's election as Executive Secretary of Christian Education. The collection continues with records from his episcopal leadership, his presidency of the N.C.C., and his involvement in the negotiations for the Uniting Conference in 1968.

This collection contains materials relating to Clymer's life after his college days at Asbury. The earliest records are correspondence, addresses/sermons, and the graduate papers from the 1940's. Clymer's correspondence, the largest quantity of the record types in the collection, covers every year from 1942 through 1993, except for about ten years between the mid-1950's and 1967. Clymer's collection of addresses, sermons, and lectures is the next largest group of records, and dates from the early 1940's through the late 1980's. The collection also contains copies of some of Clymer's publications. The original accession contained copies of his books and books in which he was a contributor, as well as articles in widely circulated journals. These have been removed and transferred to the Methodist Library, Drew University, Madison, New Jersey. The collection also contains various clippings, programs, pamphlets, reports, and photographs.