WDIO-TV first went on the air on January 24, 1966 and has transmitted from its first day in color. It immediately joined ABC, which had previously been relegated to off-hours clearances on CBS affiliate KDAL-TV (channel 3, now KDLH) and NBC affiliate WDSM-TV (channel 6, now KBJR-TV). It was owned by Frank Befera, a trained engineer who owned a chain of radio stations across northeastern Minnesota. WIRT went on the air on August 31, 1967. Befera sold channels 10 and 13 to publishers Harcourt Brace Jovanovich in 1977, but remained as president and general manager. HBJ sold the stations to Hubbard Broadcasting in 1986, and Befera retired a year later.