KZJK (104.1 ) is a broadcasting the "" in the region of . The station is owned by through the radio subsidiary .
Currently, the station's main is rated at 89,000 and is located on 's tower in the suburb of , with the city of license in the suburb of . An auxiliary transmission facility is located atop the in (where studios for the station are located, though separately).
The 104.1 frequency in the Twin Cities area signed on in . For much of its early history, the station was KRSI-FM, paired with a with the same call letters. The two stations simulcast with each other on and off through much of their existence, and finally separated when the AM station was sold separately in .
Until the mid-1990s, the station was hampered by a badly located tower. Although they were licensed to the west Minneapolis suburb of , the studios were located in Eden Prairie, while their tower was located east of the Twin Cities, in . The result was a spotty signal in parts of the metropolitan area, and it would be many years until this situation was rectified.
Partly due to signal limitations and impatient management, the 104.1 FM frequency went through many format changes throughout its history.
KRSI-FM to KFMX and back
From until , KRSI-FM played hits and as "Request Radio", simulcasting with their AM sister station. This was by far the most successful format for both stations, and in , they were the #3 station in the market, behind and .
The two stations moved away from oldies and more toward current in . In 950 AM became the first affiliate of ’s automated “Great American Country” format, as both stations moved from their location in St. Louis Park to new facilities in (which today is still home to 950 AM). The FM station broadcast in for the first time and continued with a /Top 40 hybrid format, soon changing its call letters to KFMX.
KFMX FM went through a succession of different formats and transitions throughout the rest of the decade. For a brief time, they played , going up against . They began playing music at night in , soon adopting the format full-time and becoming "Disco 104". By this time, the AM station was playing rock/Top 40 as "Musicradio I-95" (featuring a great deal of ). KFMX gave up disco in as the fad faded in popularity, and both stations switched to an /"" simulcast, with KFMX becoming KRSI-FM once again.
In , the FM station switched to , as "K-JO Country", adopting the KJJO . They were up against much competition from market leader , low-rated and soon, . KJJO was never very competitive as a country station. In September 1983, after playing "" by for 48 hours straight, they launched a new format, "Twenty Years of Rock and Roll", as "K-JO 104".
KJJO's ratings improved with their classic hits format, but the station was still not making much of an impact in the market. In , KJJO transformed yet again and introduced a format, to go head-to-head with the -leaning . They kept the KJJO call letters, and dubbed themselves "Hot Rockin' 104" (later "Rock 104"). At its peak, the hard rock format pushed KJJO into the top 10 in the local ratings. KJJO was not very consistent with the harder format, though, as they went back and forth between and mainstream . In , they picked up the heavy metal affiliation for their AM sister station.
Modern Rock KJ104
By , as mainstream started to fade in popularity, KJJO, by now a station, began adding more songs to the playlist. Eventually, KJJO ditched the heavy metal and mainstream rock altogether and became a full-fledged station. At first, they called themselves "104FM", but eventually picked up the moniker "KJ104".
During the station's modern rock run, the playlist became more and more adventurous. Over time, KJ104 garnered a lot of positive in the Twin Cities area, though ratings were still mediocre. The station's manager complained in the local media that KJ104's listeners were not filling out the ratings diaries, the results of which are used to measure a radio station's success.
Back to country as "Thunder 104"
In the summer of , KJJO publicly announced a pending switch back to country music, which was becoming very popular around the time, amid a large outcry from KJ104's dedicated fans. At 6 AM on September 8, after signing off the modern rock format by playing "" by , "Thunder 104" debuted. As a country station, ratings went up slightly, but they could not compete with the established and the soon-to-sign-on .
The two other country stations trounced Thunder 104, soon knocking them back down to the same level as the former KJ104. To set themselves apart from the heavy competition, they evolved into a format as "Classic Country 104", and ratings slightly improved. Meanwhile, several former KJ104 employees were working at bringing the much-missed modern rock format back to the local airwaves, which culminated with the debut of in April 1994. A month prior to this, hard rocker (93.7 FM) became KEGE ("The Edge"), and soon became the highest-rated modern rock station in the country, succeeding where KJJO, as KJ104, failed.
Station sold, more format changes
The country fad died down by the mid-1990s, and with K102 and BOB 100 firmly establishing themselves, KJJO bowed out of the format and flipped to on March 28, , with the KJJO finally retired and new calls KMJZ introduced. During this time, ownership transferred several times. bought both the AM and FM stations from the estate of its longtime owner , then Nationwide was bought by , which spun the station off to (which later became part of ).
On , the station changed format once again, to as "104-1 The Point" with the WXPT call letters. After gradually adding in throughout the course of 2000, they shifted to a full-fledged '80s hits format on November 17, , and rebranded as "Mix 104.1". While never a dominant station, "Mix" was a modest ratings and financial success, as the station's transmitter woes were finally resolved by the move to 's antenna array in , home to the transmission facilities of most of the area's big FM stations.
CBS Radio later sold WXPT's longtime sister station at 950 AM to a local group, which turned it into , a station.
"Mix 104.1" flipped to "Jack FM" on the morning of April 21, 2005. The first song on "Jack" was "" by .
On May 10, , three weeks after the format change, the call letters were officially changed to KZJK.
Across the country, (formerly Infinity Broadcasting) now has 4 FM stations carrying the "Jack" format, the others being in , , and .
104.1 Jack FM has a much bigger playlist than most radio stations. While many stations commonly have 200-400 songs in rotation, the Jack format is known for playlists with roughly 1,200 , reducing repetition.
The "Jack FM" "Happy Ending" Event at 5 PM on January 12, 2009 was announced frequently on the station over the few days leading up to the event. The last song played before the event was "The Last Song" by Edward Bear, a nod to both the "end" of Jack and the rumored name of the new station, The Bear.
The "Happy Ending" culminated as a promotional gimmick to advertise for Jack FM's hour-long commercial-free hour to air each weekday starting at about 5 PM Central Time.
It is also noted that unlike most adult hit stations that only play recurrents and recent oldies mixed in with classic hits, this station plays at least one current hit an hour to better compete with more current based competiters and .
KZJK offered an HD2 subchannel that used to air a format, somewhat of a revival of the old KMJZ. Smooth jazz was also on 100.3 FM for several years as KJZI, prior to the station switching to as in late 2005.
Due to the demise of sister station "" on December 26, 2011, 104.1 HD2 flipped to on that same day, as Lite FM flipped to . 102.9 instead flipped on December 25 at 6:00 p.m., about 14 hours earlier than originally planned. The switch from smooth jazz to "Lite FM" also occurred at this time.