Numbered among Nebraska's most influential modern artists, Thiessen had a career as an artist, art critic, art administrator, scholar and teacher. Though he traveled a great deal, he always returned to the house his family purchased on Stone Avenue in Omaha, in 1913. He studied art briefly at the University of Omaha, but grew impatient with its conservative curriculum and came to Lincoln to continue his studies at the School of Fine Arts at the University of Nebraska. There his instructors included Dwight Kirsch, and his circle of friends included the artist Louise Austin (a former Munich student of abstract expressionist painter Hans Hoffman), and writers Mari Sandoz, Dorothy Thomas, Kenetha Thomas, Weldon Kees, and Loren Eiseley. He studied architecture and design, rather than "serious painting."
Thiessen embarked on what looked to be a very successful commercial career as an interior designer and decorator, but in Paris in 1929, hearing for the first time about the New York stock market crash, he decided to remain in Europe for a time. He began, finally, to study serious painting, briefly, in Paris, and again, briefly, at the Heatherly School of Art in London. In 1932, he was accepted as a student at the Swedish Royal Academy of Fine Arts in Stockholm, with intermittent travel breaks, he studied there until he gained his diploma in 1938.
He returned to Nebraska, where his work found recognition in two important shows, one in 1938 in Morrill Hall in Lincoln, where Mari Sandoz lent her support, and a large 1939 exhibition at the Joslyn Museum in Omaha. In 1941 he found an appointment as Assistant to the Director, then as Director of the WPA's Iowa Federal Arts Project. He served until the Project was closed down in 1942 and he enlisted in the Air Force for the duration of the war.
Theissen served as the Omaha World-Herald regular art critic and arts columnist from 1938 to 1950, then took a break and returned as art critic in 1963. He was a founder and the first Executive Secretary of the Nebraska Arts Council (1966-1974), he played an important supporting role in the creation of the Sheldon Museum of Art in Lincoln and MONA, the Museum of Nebraska Art in Kearney, and he taught numerous students at UNO and other institutions. He was above all a powerful artist, but nonetheless, with characteristic generosity, as Sheldon Art Gallery Director Norman Geske recognized at his death, Thiessen "gave an awful lot of his life and energies to the arts in the state."
MONA, which has a Thiessen collection, has an excellent and more detailed on-line biographical sketch of the artist.
Anyone with a local interest in the artist should read Leo Adam Biga's on-line article, "Leonard Thiessen social justice triptych deserves wider audience" about Thiessen's "Crucifixtion" triptych in the Church of the Resurrection at 3004 Belvedere Boulevard in Omaha. In this connection, former Omaha resident and Theissen biographer William Wallis, Prairie Symphony: The Story of Charles Leonard Thiessen brings up the effect on Thiessen of the Omaha race riot of 1919. Wallis was a close, and well-informed friend of Theissen. Theissen was co-designer of the Pershing Auditorium mosaic in Lincoln.
