WNAC-TV first signed on the air on June 21, 1948, as the second television station in Boston after WBZ-TV (channel 4), which debuted twelve days earlier.
Channel 7 originally operated as a CBS affiliate, but also carried some programs from the ABC and the now-defunct DuMont Television Network.
The station was originally owned by General Tire, along with WNAC radio (then at 1260 AM, frequency now occupied by WBIX; later moved to 680 AM, now WRKO), which served as the flagship station of the Yankee Network, a regional New England radio network.
General Tire had purchased the Yankee Network in 1943.
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.

In 1950, General Tire bought the West Coast regional Don Lee Broadcasting System.
Two years later, it acquired the Bamberger Broadcasting Service (owners of WOR-AM-FM-TV in New York City) and merged its broadcasting interests into a new division, General Teleradio.
General Tire purchased RKO Radio Pictures in 1955 after General Tire found that RKO's film library would be a perfect programming source for WNAC-TV and its other television stations.
The studio was merged into General Teleradio to become RKO Teleradio; after the film studio was dissolved, the business was renamed RKO General in 1959.

By 1955, ABC began to increase the amount of programming seen as "secondary clearances" on channel 7, which continued until the original incarnation of WHDH-TV signed on over channel 5 in 1957.
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 the aforementioned channel 5 signing on as an independent station, but Storer's purchase of channel 9 never materialized as outcry from New Hampshire viewers led regulators to reject its request to build a new tower near Haverhill; Storer eventually purchased WIHS-TV (channel 38) in 1966 and changed its call letters to WSBK-TV.
The station also had a secondary affiliation with the Paramount Television Network; in fact it was one of that company's strongest affiliates, carrying Paramount programs such as Time For Beany, Dixie Showboat, Hollywood Reel, and Armchair Detective.
From 1948 to 1950, WNAC-TV shared the rights to Boston Braves game telecasts with WBZ-TV; and shared rights to Boston Red Sox telecasts with WBZ-TV from 1948 to 1954.
In the fall of 1948, WNAC-TV became the first station to televise games of the Boston Bruins, carrying the third period (and sometimes the second and third periods) of home games.

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.
As a preemptive move, CBS decided to move its Boston affiliation to WHDH-TV when the changeover became official.
However, final approval of the RKO-NBC deal was held up at the Federal Communications Commission (FCC) and the U.S. Department of Justice due to issues involving NBC's ownership of WRCV-AM-TV in Philadelphia, which RKO would acquire in the trade.
Meanwhile, WNAC-TV reached an agreement to carry ABC programs in what was thought to be an interim arrangement.
The affiliation swap between WNAC-TV and WHDH-TV went into effect on January 1, 1961.
Ultimately, the RKO-NBC transaction never materialized, and channel 7 would remain an RKO-owned ABC affiliate for the next eleven years.

In 1969, the Boston Herald-Traveler Corp., WHDH-TV's parent company, lost its license to operate channel 5.
Boston Broadcasters, Inc., the owners of the station that replaced it, WCVB-TV, planned to air more local programming th
WNAC-TV first signed on the air on June 21, 1948, as the second television station in Boston after WBZ-TV (channel 4), which debuted twelve days earlier. Channel 7 originally operated as a CBS affiliate, but also carried some programs from the ABC and the now-defunct DuMont Television Network. The station was originally owned by General Tire, along with WNAC radio (then at 1260 AM, frequency now occupied by WBIX; later moved to 680 AM, now WRKO), which served as the flagship station of the Yankee Network, a regional New England radio network. General Tire had purchased the Yankee Network in 1943. 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.
In 1950, General Tire bought the West Coast regional Don Lee Broadcasting System. Two years later, it acquired the Bamberger Broadcasting Service (owners of WOR-AM-FM-TV in New York City) and merged its broadcasting interests into a new division, General Teleradio. General Tire purchased RKO Radio Pictures in 1955 after General Tire found that RKO's film library would be a perfect programming source for WNAC-TV and its other television stations. The studio was merged into General Teleradio to become RKO Teleradio; after the film studio was dissolved, the business was renamed RKO General in 1959.
By 1955, ABC began to increase the amount of programming seen as "secondary clearances" on channel 7, which continued until the original incarnation of WHDH-TV signed on over channel 5 in 1957. 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 the aforementioned channel 5 signing on as an independent station, but Storer's purchase of channel 9 never materialized as outcry from New Hampshire viewers led regulators to reject its request to build a new tower near Haverhill; Storer eventually purchased WIHS-TV (channel 38) in 1966 and changed its call letters to WSBK-TV. The station also had a secondary affiliation with the Paramount Television Network; in fact it was one of that company's strongest affiliates, carrying Paramount programs such as Time For Beany, Dixie Showboat, Hollywood Reel, and Armchair Detective. From 1948 to 1950, WNAC-TV shared the rights to Boston Braves game telecasts with WBZ-TV; and shared rights to Boston Red Sox telecasts with WBZ-TV from 1948 to 1954. In the fall of 1948, WNAC-TV became the first station to televise games of the Boston Bruins, carrying the third period (and sometimes the second and third periods) of home games.
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. As a preemptive move, CBS decided to move its Boston affiliation to WHDH-TV when the changeover became official. However, final approval of the RKO-NBC deal was held up at the Federal Communications Commission (FCC) and the U.S. Department of Justice due to issues involving NBC's ownership of WRCV-AM-TV in Philadelphia, which RKO would acquire in the trade. Meanwhile, WNAC-TV reached an agreement to carry ABC programs in what was thought to be an interim arrangement. The affiliation swap between WNAC-TV and WHDH-TV went into effect on January 1, 1961. Ultimately, the RKO-NBC transaction never materialized, and channel 7 would remain an RKO-owned ABC affiliate for the next eleven years.
In 1969, the Boston Herald-Traveler Corp., WHDH-TV's parent company, lost its license to operate channel 5. Boston Broadcasters, Inc., the owners of the station that replaced it, WCVB-TV, planned to air more local programming th
WNAC-TV (Boston)