WMTW signed on September 25, 1954 as the third television station in the Portland market and under the ownership of Mount Washington Television, a group that included former Maine Governor Horace Hildreth. It has always been an ABC affiliate although it aired some DuMont programming in its first year. The station's sign-on made Portland one of the smallest markets in the United States with three network affiliates on the analog VHF band. WMTW is also the longest-tenured primary ABC affiliate in New England. The WMTW call sign was modified to include a "-TV" suffix on September 1, 1958.