Charles "Carl" Bohnen was born in October 1872 (according to the U.S. Census) in Erie, Pennsylvania, to Nicholas and Marie Jochin Bohnen, who had emigrated from Germany. The family moved to Meyer's Grove, Minnesota in the following year.
Carl Bohnen graduated from St. John's University at Collegeville, Minnesota in 1892, earning a diploma in "Bookkeeping and Penmanship." Soon afterwards, he met Jake Hohman who employed him in a business involving drawing portraits from photographs. In 1896, Bohnen established a studio in St. Paul, Minnesota, where he continued creating portraits from photographs. During this time, he met Charlotte Johnson, whom he married in 1898.
Bohnen moved his studio in 1902 and began painting portraits from life. Paul Manship's family were neighbors of the Bohnens at Bald Eagle Lake near St. Paul, Minnesota. Bohnen studied at the Minnesota School of Fine Arts in exchange for cleaning up the classrooms. He later made space available to Manship in his studio.
In 1904, Bohnen completed studies at the St. Paul Art Institute. He also did commercial work, including doing portraits of sports figures for the St. Paul Pioneer Press and Dispatch. Through his newspaper connections, he did portraits of many other celebrities, later selling reproductions of these artworks. Eventually, he was hired as a portrait painter by a variety of prominent sitters, including R. A. Jackson, a railroad executive in St. Paul. An exhibition of Bohnen's portraits organized by Jackson resulted in additional commissions.
Through R. A. Jackson, several lumber millionaires helped finance a European trip for the Bohnen family in 1914. Bohnen studied at the Koenigliche Kunst Academie in Munich under Carl Von Marr and Angelo Jank, and established a studio in that city. Travel constraints resulting from the onset of World War I caused the family to remain in Munich for three years. During this time, Bohnen was a member of the American Artist Club that included E. Martin Hennings, Louis Grell, and Emil Frei.
Bohnen and his family returned to St. Paul, Minnesota in May 1918, where he established a studio. He moved to Chicago in the following year, opening a studio in the Fine Arts building where he remained until the 1930s. Bohnen created thousands of portraits primarily of notable people including Edward the Prince of Wales, Ethel Barrymore, Enrico Caruso, Helen Hayes, Charles Lindbergh, Douglas MacArthur, John McCormack, Cardinal Mundelein, and Lawrence Tibbett.
In 1928, Bohnen established a studio in Paris and worked there sporadically through 1933. In 1933, he returned to St. Paul, Minnesota, setting up his studio in the Ryan Hotel. In 1944, he retired to live in Los Angeles, California, with his son, actor Roman Bohnen. After his son's sudden death in 1949, Bohnen lived with his other son, Arthur, in Chicago.
Carl Bohnen died on December 31, 1951 in Willmette, Illinois.