The station first signed on the air on November 14, 1965 as KAAR. It was the first television station in the San Diego market to operate on the UHF band and was the market's first independent station. The station originally operated from a building that was once occupied by the National Pen Company, located in the neighborhood of Kearny Mesa, 10 miles (16 km) northeast of downtown San Diego. The station signed off on June 12, 1967; Channel 39 was then sold to Western Telecasters Inc., controlled by the Texas-based Bass family, and returned to the air on February 2, 1968 as KCST (standing for "California San Diego Television").
For a four-year period from the late 1960s to the early 1970s, Western Telecasters tried to take the ABC affiliation from XETV (channel 6) – a station licensed across the Mexican border in Tijuana but which broadcast exclusively in English, with a studio facility based in San Diego. XETV had been San Diego's ABC affiliate since 1956 under a special arrangement between the Federal Communications Commission and Mexican authorities, subject to renewal by the Commission every year. Upon the FCC granting its annual renewal to ABC/XETV in late 1968, Western Telecasters countered, claiming that the presence of KCST made it no longer necessary for an American television network to affiliate with a Mexican television station.
In May 1972, the FCC revoked XETV's permission to carry ABC programming. As the only other commercial station in the market other than CBS affiliate KFMB-TV (channel 8) and then-NBC affiliate KGTV (channel 10), KCST took over the ABC affiliation in two stages: daytime programming moved to channel 39 in June 1973, followed by primetime programs and all other shows (including children's programs, network newscasts and sports) by July 1, 1973. Four months earlier in March, Western Telecasters agreed to sell KCST to Storer Broadcasting, which owned major network affiliates in the Eastern and Midwestern United States. The sale was completed on September 30, 1974; shortly afterwards, Storer added a "-TV" suffix to the KCST callsign. The switch and sale changed channel 39's fortunes, transforming the low-rated independent into a major player in the market. Riding on the heels of ABC's ascent to first place nationally during the 1975-76 season, KCST also out-rated its network-affiliated rivals locally. XETV, meanwhile, operated as an independent station until October 1986, when it became a charter affiliate of the Fox Broadcasting Company.
On June 27, 1977, in the wake of its new success as the highest-rated television network in America, ABC moved its San Diego affiliation from KCST to KGTV, causing an affiliation swap that ended with KCST taking the NBC affiliation formerly held by KGTV.
In 1985, the Storer stations were acquired by Kohlberg Kravis Roberts & Co.. Two years later, KCST and the other Storer stations were sold to Gillett Communications (former Storer flagship WTVG in Toledo, Ohio, was the only station left out of the sale and was instead sold to a local employee/investor group). On September 16, 1988, the station changed its call letters to KNSD, and adopted the on-air brand "Channel 7/39" (in respective reference to its cable and over-the-air channel positions). Gillett was restructured into SCI TV in 1991, after Gillett defaulted on some of his bond purchases. After SCI filed for Chapter 11 bankruptcy in 1992, the company's stations were sold in a group deal to New World Communications.
New World subsequently entered into a deal with News Corporation that would result in most of New World's television stations (which were primarily CBS affiliates, along with a few ABC and NBC stations) switching from their "Big Three" network affiliations to join Fox, causing the network's affiliations in the affected markets relocating from UHF to VHF stations. However, KNSD retained its NBC affiliation since Fox's San Diego affiliation was already on the VHF band through XETV. New World sold KNSD and WVTM-TV in Birmingham, Alabama to NBC in May 1996; the sale was finalized that August. Following the sale's closure, in January 1997, KNSD modified its on-air branding to "NBC 7/39". In October 1997, NBC sold a 24% ownership interest in KNSD to LIN Television; in exchange, NBC acquired majority control (76%) of its Dallas/Fort Worth affiliate KXAS-TV from LIN. The deal closed on March 2, 1998, marking the official launch of the new NBC/LIN joint venture known as Station Venture Operations, LP (which was controlled by NBC).
Under the traditional definition, KNSD is the only owned-and-operated station of a major network in the San Diego market (however, several stations owned by Grupo Televisa on the Mexico side of the market are O&Os of that company's various networks). The station blamed its woes on its UHF status in the past, but as viewers migrated to cable television (San Diego has one of the highest cable penetration rates in the United States), along with the fact that most of the market's UHF stations brand by their cable channel placements or call letters rather than by their physical channel, along with VHF analog stations operating their post-transition digital signals on the UHF band, the issues with its position on the UHF dial have been reduced. KNSD had formerly owned low-power station KNSD-LP (channel 62), which was leased to Entravision Communications to expand the coverage area of Univision affiliate KTCD-CA (channel 17, now KBNT-CD).
In the spring of 2001, KNSD moved its operations into the NBC Building, a high-rise office building in downtown San Diego that was redeveloped to serve as its studio and office facilities, which includes a glass-enclosed street-level news studio resembling that of the streetside studio at Rockefeller Center in New York City used by NBC's Today. In February 2013, LIN Media withdrew itself from the Station Venture Operations joint venture as part of a corporate reorganization. As a result, NBC regained full ownership in KNSD and gained full ownership of KXAS.
On January 9, 2014, KNSD announced that it would not renew its lease for the 225 Broadway studios when it expires in 2016. On June 23, the station announced the purchase of a two-story, 50,000 square feet (1.1 acres) building at the StoneCrest office complex on Granite Ridge Drive in the Kearny Mesa neighborhood for $9.6 million, which will be converted into a new facility for the station. The location was chosen due to its easy access to San Diego County’s main thoroughfares, and no-cost parking for its employees. The studio opened on February 29, 2016.
In January 2017, NBC announced that it is hiring people for KNSD with the intention of launch a new Telemundo O&O station in San Diego on its second subchannel (that will be branded as "Telemundo San Diego") replacing Mexican-licensed station XHAS-TDT (whose affiliation will expire in June 2017), and will move Cozi TV to the third digital subchannel.
On March 15, 2016, NBCUniversal's parent company Comcast pulled the signals of KNSD along with co-owned cable channels USA Network, Bravo, Syfy, MSNBC and CNBC from Dish Network systems in the San Diego area as a result of a dispute between NBC and Dish; despited that Dish is clamming NBCUniversal is demanding to renew its carriage of 10 NBC-owned stations and 16 Telemundo-owned stations including those removed due to the dispute. Telemundo station XHAS-TDT was unaffected by that said dispute. Three days later on March 18, 2016, the company announced it will continue to carry KNSD and five other cable channels for another 10 days while the FCC is seeking arbitration.
On December 31, 2016, 10 months after the Dish-NBC dispute, NBCUniversal announced they wanted to blackout the signals of KNSD due to a carriage dispute with Spectrum (formerly Time Warner Cable) in San Diego, its first with that provider in 15 Years. This dispute involved 6 NBC owned-and-operated stations (including KNSD and and sister stations KNBC in Los Angeles, WNBC in New York, WVIT in Hartford, WMAQ-TV in Chicago and KXAS-TV in Dallas), 3 Telemundo owned-and-operated stations (including WNJU in New York, KVEA in Los Angeles and KXTX-TV in Dallas), USA Network, Syfy, Bravo, CNBC, MSNBC, NBCSN, E!, Oxygen and the other NBCU-owned cable channels. If a deal wasn't in place, the affected stations and cable channels would've been removed from Spectrum systems across the country. Telemundo station XHAS-TDT was unaffected by the said blackout. On January 18, 2017, KNSD and the other cable channels were return to the Spectrum cable systems in San Diego following Spectrum and NBCUniversal struck a new carriage deal.
The station's digital channel is multiplexed:
On December 20, 2012, KNSD (as well as NBC's owned-and-operated stations) began carrying Cozi TV, a network focusing on classic television programming, which replaced NBC (California) Nonstop (which had aired on the subchannel since 2011) on digital subchannel 39.2.
KNSD shut down its analog signal, over UHF channel 39, on February 17, 2009, the original target date in which full-power television stations in the United States were to transition from analog to digital broadcasts under federal mandate (which was later pushed back to June 12, 2009). The station's digital signal remained on its pre-transition UHF channel 40. Through the use of PSIP, digital television receivers display the station's virtual channel as its former UHF analog channel 39.
As part of the SAFER Act, KNSD kept its analog signal on the air until June 26 to inform viewers of the digital television transition through a loop of public service announcements from the National Association of Broadcasters.
As an NBC owned-and-operated station, KNSD carries the entire NBC schedule. Syndicated programs broadcast by the station include Access Hollywood, Steve Harvey, Ellen, Wheel of Fortune and Jeopardy! among others. The first three are distributed by NBC's parent company, while these latter two are distributed by CBS Television Distribution, making it the only NBC O&O to carry these game shows in the 7 p.m. hour on weeknights.
Local lifestyles and infotainment program Streetside San Diego and Spanish-language newscast Noticias Mi San Diego (the latter of which was a holdover from KNSD's operation of KBOP-CA (channel 43, now KSEX-CD)) were local programs previously produced by KNSD; these programs, along with the station's weekend morning newscasts (which were restored in December 2013 as part of a gradual newscast expansion resulting from a benefits package offered to the FCC upon the NBCUniversal-Comcast merger), were canceled on December 5, 2008 as a result of budget cuts at the station. The station currently produces a late-night music and lifestyle program SoundDiego on Saturdays.
KNSD presently broadcasts 36½ hours of locally produced newscasts each week (with 6½ hours on weekdays and 2 hours each on Saturdays and Sundays); however during the NFL season, the Sunday edition of the 6:00 p.m. newscast is typically preempted due to NBC Sunday Night Football coverage and the Thursday edition of the 4:00 p.m. newscast is reduced to 30 minutes and the 5:00 p.m. and 6:00 p.m. newscasts are typically both preempted due to Thursday Night Football coverage. In addition, the station produces the sports highlight program Jerome's Furniture SportsWrap, which is sponsored by local furniture store Jerome's Furniture and airs Sundays after the 11:00 p.m. newscast.
As KCST, the station started its news department in 1973; Harold Greene, who would later gain fame as an anchor in Los Angeles, served as its news director and lead news anchor. As a newcomer, channel 39's newscasts regularly placed third in the market, behind KFMB and KGTV, for many years. On October 28, 2005, KNSD began producing a nightly half-hour 10:00 p.m. newscast for WB affiliate KSWB-TV (channel 69, now a Fox affiliate), following owner Tribune Broadcasting's decision to shut down KSWB's in-house news department (KSWB continued to produce local news updates during its simulcast of Los Angeles sister station KTLA's weekday morning newscast from the station's Kearny Mesa studios). KNSD's news outsourcing agreement with KSWB ended on July 31, 2008, when that station resumed in-house news operations upon switching its affiliation from The CW to Fox.
In June 2009, the station outsourced production of its evening weather forecast segments to Los Angeles sister station KNBC, using that station's on-air weather staff; as a result, KNSD became the only network-owned station in the United States and one of the few television stations in North America to outsource weather forecasts to a co-owned station. In October 2011, KNSD resumed in-house production of its forecast segments with the hiring of three weather anchors (including chief weather anchor Dagmar Midcap, who joined the station from WGCL-TV in Atlanta) and the promotion of Jodi Kodesh from reporter to morning weather anchor. On December 13, 2010, KNSD unveiled a new HD-ready set for its newscasts, which mainly mirrors that of the "Window on the World" set used by Today; this marked the first major renovations since KNSD moved into the NBC Building in 2001.
On January 29, 2011, KNSD became the fifth television station in the San Diego market, and the last NBC-owned station to begin broadcasting its local newscasts in high definition; footage shot in-studio is broadcast in high definition, while all news video from on-remote locations was initially broadcast in standard definition. The station also implemented a new logo and on-air graphics package designed by NBC Artworks and the advertising agency Mother New York, which dropped the longtime "NBC 7/39" brand in favor of branding as simply "NBC San Diego". The "block" graphics and branding used in this period (which featured similarities to the design of the NBC Nonstop channels) were to be implemented by the remaining NBC O&Os (and were used by their websites during the same period); however, KNSD was the only O&O to use the scheme on-air before dropping it in July 2012, in favor of Artworks' new "Look F" standardized graphics that were first adopted by sister station KNTV (at which point, the station revised its branding to "NBC 7 San Diego"). On October 25, 2012, the station expanded its weekday morning newscast to 2½ hours, with the addition of a 4:30 a.m. half-hour.
On July 18, 2016, KNSD began using the new "Look N" standardized graphics. the graphics was first implemented by the NBC O&Os in the East Coast in Summer of that year; however, KNSD became the second NBC O&O in the West Coast to begin using the new graphics. also, its theme music is also updated, by warp-speeding the NBC chimes in the "LA Groove" theme in all of its opens, making the first NBC-owned station to warp-speed its musical signature in their theme music. prior to the graphics change, KNSD along with sister stations KNBC and KNTV revamped their websites on July 1, 2016.
On January 3, 2017, KNSD expanded the 11:00 a.m. midday newscast to an hour, following rivals KGTV and KFMB-TV. As a result of this expansion, the station moved the entertainment newsmagazine program Access Hollywood to the overnight slot of 2:05 a.m. and they subsequently pre-empted the network's rebroadcast of the fourth hour of Today.Mark Mullen – anchor
Dagmar Midcap – chief meteorologist
Jim Laslavic – sports director
Emily Chang - reporter (later at CNN and Bloomberg Television)
Courtney Friel (later at KTTV in Los Angeles, now at KTLA in Los Angeles)
Harold Greene - anchor (1973–1974; now retired)
Roger Hedgecock - anchor (1991–1992, now a radio host at KOGO-AM)
Joe Lizura - weather/meteorologist (1990–2006, subsequently at KUSI)
Bill Ritter - Reporter (now at WABC)
Rolland Smith - anchor (1993–1996, returned to New York)
Anne State - anchor/reporter (2002–2008, later at WBBM-TV in Chicago and WITI in Milwaukee, recently left KOIN in Portland, Oregon for San Diego rival KGTV)
Lou Waters - news director and anchor (subsequently an early and tenured CNN anchor)