WNBH has often claimed to be one of the oldest broadcast radio stations in America; it has asserted that it was the 11th oldest in the USA, going back to May 21, 1921; but there is no evidence to support that assertion. According to the Department of Commerce records, WNBH received its license in November 1925. When WNBH went on the air, it had its studios at the New Bedford Hotel, from whence it derived its call letters. An early transmitting antenna for the station was lifted onto the chimney of Atlas Tack Company in Fairhaven by using helium-filled balloons. When the rig was in the right spot, the balloons were deflated by shotgun blasts. The operation took place at 5AM with the gunshots prompting neighbors to call the police.
On July 1, 1932, The Federal Radio Commission authorized WNBH to increase its daytime power from 100 W to 250 W. Output remained at 100 W for night transmissions.
WNBH's original station manager was a pioneer in amateur radio, Irving Vermilya. Vermilya had put an earlier station on the air in New Bedford in May 1922, WDAU. When WDAU's owners got out of the broadcasting business, Vermilya was asked to manage WNBH. In 1948 WNBH added FM service with WNBH-FM on 98.1 Megacycles (as the term was known at the time and later became Megahertz)/Channel 251 (now WCTK). The two stations are still co-owned to the present.