The KMNF-LD license originated as K38MY-D in St. James, Minnesota, a translator for KEYC-TV (then owned by United Communications) on UHF channel 38[5] that signed on in March 2012.[6] K38MY-D went off the air on December 21, 2017, after the expiration of its tower lease agreement with BENCO/CTV; KEYC had operated UHF translators from Cooperative TV's Godahl tower since 1993.[7]
K13AAR-D was included in Gray Television's 2019 purchase of United Communications' television stations.[12]
On May 23, 2019, the station was granted a construction permit to move to channel 7 as K07AAH-D;[13] on June 3, 2019, the call letters were changed to KMNF-LD, a close match for those originally proposed for sister station KEYC-TV in 1958.[14]
On June 24, 2019, Gray announced that KMNF-LD would launch as early as September as an NBC affiliate, with The CW on its second subchannel.[4][15] KEYC-TV itself had launched in 1960 as an NBC affiliate, switching to CBS in 1961.[4] For the next 58 years after that, NBC programming was not available over-the-air in the Mankato market. Since 1981, Minneapolis affiliate KARE and Rochester affiliate KTTC had served as the default NBC affiliates for southwestern Minnesota via cable. KMNF-LD's sign-on leaves ABC and PBS as the only networks to not have over-the-air affiliates in Mankato; ABC programming is carried on cable via KSTP-TV and KAAL, and PBS programming carried via KTCA-TV; with KSTP and KTCA being carried on CTV translators K30FN-D (KSTP) and K26CS-D (KTCA) in St. James.[16][17][18][19]
Testing on KMNF-LD began on October 28, 2019.[20] The station officially signed on December 1, 2019.[21]
On January 17, 2023, KMNF-LD began broadcasting translator K33MW-D from the KEYC-TV studio tower.[22]
KMNF-LD began simulcasting some KEYC newscasts on December 2, 2019. KEYC News Now This Morning airs weekdays from 5:30 to 7 a.m. on both KEYC-TV and KMNF-LD. The stations also simulcast the 10 p.m. news on weeknights, with each station airing separate commercials during each simulcast.
On February 21, 2022, KMNF-LD began simulcasting KEYC's 6 p.m. newscast.
On September 3, 2023, KMNF-LD began airing a 5 p.m newscast on Sunday evenings.