Professor Knowler has been a leader in the development of courses in the areas of actuarial science, statistical quality control and biostatistics.
He joined the U of I faculty in 1939 after two years as an instructor at Hunter College and has taught continuously, since then, with the exception of one year which he spent in India as an advisor for the U.S. Department of State.
During his time at the U of I, he taught in the Department of Mathematics and Astronomy and the Division of Mathematical Sciences, and from 1945 until the present, he has been a member of the faculty of the U of I Department of Preventive Medicine and Environmental Health.
He served as chairman of the U of I Department of Mathematics and Astronomy from 1946 to 1959.
Among the many professional organizations in which Knowler holds membership are the American Academy of Actuaries and the American Society of Pension Actuaries, where he is a fellow and certified pension consultant, as well as a member of the board.
A fellow and founding member of the American Society for Quality Control, in 1962 that organization gave Knowler its highest award—the Shewhart Medal. He is a fellow of the Iowa Academy of Science and a member of the Midwestern Actuarial Forum.
A scholarship endowed by businessmen was established in Knowler's name in 1961, to be given alternately to U of I students in science, engineering or administration.
Knowler is a member of the Iowa City Rotary Club, serving as treasurer, board member and as president in 1973-74. He is also governor-elect of District 600 of Rotary International and will be governor in 1980-81.
Since 1969 Knowler has served on the board of directors of Xi of Theta Xi Alumni Association.
He has served on the board of directors of Blue Shield of Iowa since 1966, on the executive committee since 1968 and was named treasurer in 1979. he also served as a member of the joint finance and joint management committees of Blue Cross and Blue Shield of Iowa.