Originally established in 1948, WNAC-TV signed off for the final time at 1 a.m. on May 22, 1982, due to improprieties by its parent company; it was replaced that morning with WNEV-TV (now WHDH), which operates on a separate license.

WNAC-TV first broadcast from the WNAC/Yankee Network's studios at 21 Brookline Avenue, near Fenway Park, before RKO moved its Boston operations to new facilities near Government Center at 40 Hawkins Street (later renamed 7 Bulfinch Place) in 1968.

However, WNAC-TV was in danger of losing its CBS affiliation that same year when Storer Broadcasting (which had very good relations with CBS) planned to purchase WMUR-TV (channel 9) in nearby Manchester, New Hampshire, and move its transmitter to just outside Haverhill, Massachusetts, only 20 miles north of Boston; approval of the move would have potentially made WNAC-TV a full-time ABC affiliate and resulted in channel 5 becoming an independent station.

However, Storer's purchase of channel 9 never materialized following an outcry from New Hampshire viewers that led regulators to reject its request to build a new tower near Haverhill.

Storer eventually entered Boston with its purchase of UHF station WIHS-TV (channel 38) in 1966, changing its call letters to WSBK-TV.

WNAC-TV was nearly sold by RKO General, along with its radio sisters, to NBC as part of a multi-city transaction and station trade between the two companies announced in March 1960.

[8] However, final approval of the RKO-NBC deal was held up at the Federal Communications Commission (FCC) and the U.S. Department of Justice because of issues involving NBC's ownership of WRCV-AM-TV in Philadelphia, which RKO would acquire in the trade.

An appeals court partially reversed the ruling and ordered new hearings for the Los Angeles and New York licenses, finding that the FCC had overreached in connecting them to WNAC-TV's renewal.

[15] On the evening of May 21, 1982, RKO General’s final full day of operating WNAC-TV, the station preempted CBS’s primetime schedule to broadcast Game 6 of the NBA Eastern Conference Finals between the Boston Celtics and the Philadelphia 76ers (a production of CBS Sports which aired on tape-delay over the rest of the network later that evening).

This fact greatly appealed to CBS when it decided to abandon the original WHDH-TV (which would return to the air under the callsign WCVB) in 1972 and re-affiliate with WNAC.

Ted O'Brien, who had replaced Scarborough as the station's primary anchor, remained as lead anchor until being paired with Jay Scott, a young reporter who was hired with a publicity campaign claiming that the news director, on a nationwide talent hunt, had found Scott in a hotel room in Denver, where he had watched television looking for talent.

Henning was joined on WNAC's newscasts by station standbys Eddie Andelman and Dr. Fred Ward and reporters Gary Armstrong, Gayle Sinibaldo, Charlene Mitchell, Tanya Hart, Mike Levine, and Sheila Fox.

The RKO licensing difficulties over the next few years were accompanied by a drop in the ratings, caused by overall leadership instability with multiple general managers and news directors revolving in and out of 7 Bulfinch Place.

WCVB's large-scale public service and news division remit, and a commitment to put the tarnished image of the former channel 5's licensee in the rear view, also easily overwhelmed WNAC.

During a December 1977 broadcast, anchor Jack Cole quipped sardonically that "We'll be back with more alleged news" following a report on how to chimney sweep in advance of the arrival of Santa Claus.

[24] In the year leading up to RKO's sale of channel 7's assets to David Mugar after losing its licensing appeal, the station hired Susan Brady to co-anchor with Brad Holbrook.

After RKO's loss of the WNAC license in 1980 was upheld by the Federal Court of Appeals for the District of Columbia, Brady left for a position in Los Angeles.

She was quickly replaced by young weekend anchor Susan Burke, who worked with Holbrook both during the transition from RKO to New England Television and for the first months of the new ownership.