Brother Leonard A. Mann, S.M., Ph.D., a native of Cleveland, Ohio, graduated from Mount St. John Preparatory School in 1933 and received a bachelor's degree in education from the University of Dayton in 1936. Brother Mann began his teaching career in 1936 at Chaminade High School in Dayton, and subsequently taught at St. John the Baptist High School in Philadelphia (1937), Chaminade High School in Santa Cruz, California (1937-38), St. Joseph's High School in Alameda, California (1938-39), Mount St. John Preparatory School in Dayton (1939-43); Holy Trinity High School in Sioux City, Iowa (1943-44), Hamilton Catholic in Hamilton, Ohio (1945-47), and North Catholic in Pittsburgh (1952-54). Brother Mann earned a master's degree in physics at The Ohio State University and a doctorate in physics at Carnegie Tech, Pittsburgh, in 1954.

Brother Mann began his association with the University of Dayton as a professor of physics in 1954. He soon became chairperson of the department and shortly thereafter was appointed to serve as the dean of the College of Arts and Sciences in 1959. A gifted teacher, he also gave strong administrative leadership to the University by building the modern foundation for the College of Arts and Sciences. For more than two decades, Bro. Mann provided the patient hand and steady guidance that built the academic reputation of the College. Under his leadership as dean, Brother Mann was instrumental in helping form many new academic programs, including a doctoral program in biology, the first Ph.D. program at the University of Dayton. Brother Mann served as dean until 1980 when he retired from administration and returned to teaching, a labor of love characterized by a selfless commitment to students.

In 1991, Brother Mann was honored by the university as a senior retiree. Dr. Michael O'Hare, chairperson of the Department of Physics, described Brother Mann as a true servant-leader in the Marianist tradition. "He served his church, his order, his colleagues, and most of all his students." At the time of his death in 1995, Brother Mann had served as a Marianist brother for 61 years. The Bro. Leonard A. Mann, S.M., Ph.D., Chair in the Sciences was established to recognize his outstanding example of the Marianist spirit and commitment to excellence.