The group was first mentioned by the press in late 2008, when rumours were spreading that YG was creating a female version of Big Bang named Sista. In response to those rumours, YG Entertainment President Yang Hyun Suk stated that the name was not chosen yet. In January 2009, it was announced that the "Female Big Bang" would debut around July 2009 with three members — CL, Park Bom, and Minzy. Later that month, YG stated that Sandara joined the group, with one more member to follow. In the end, YG Entertainment announced that the group would consist of four members and debut sometime in May 2009. The company stated that the group had trained for 4 years, and that their debut album would contain songs produced by Teddy Park. The group's name was initially announced as "21"; however, due to the discovery of a singer with the same name, the group was quickly renamed "2NE1".
Park Bom revealed that the group was originally planned by YG Entertainment to be a 3-member group with herself, Koo Hye-sun, and Sandara.
Early 2009- Mid 2009: Introduction and debut
2NE1's first song was "Lollipop", digitally released on March 27, 2009. The song was created for LG to promote their Cyon phone, and it was a joint release with Big Bang; the commercial/music video debuted on March 28, 2009. Although it was not a promoted single (as it was an advertisement song, there were problems with network chart eligibility), "Lollipop" proved to be a strong chart hit, going to #1 on various online charts and topping music television network M.Net's online chart for four weeks in a row. It was also profiled in Perez Hilton's blog. However, questions were raised about the group's future, as the song's success was attributed to the popularity of Big Bang.
On April 30, Yang Hyun-suk revealed that 2NE1's debut song would be a hip-hop/reggae song, and that it would be digitally released on May 6, 2009. Titled "Fire", the song was fully written and produced by 1TYM's Teddy Park. Teasers of the song were released on their official website at the beginning of May, with a 20-second clip released on May 1.
"Fire" was released as planned on May 6, with two versions of the music video — a "space" version and a "street" version — released the same day. The videos received over one million views in a day; the viewcount then increased to two million. The group's first performance of the song was on May 17, 2009, on SBS's Inkigayo, beginning the group's activities. Perez Hilton commented that "Fire" definitely lives up to the title, even including their first performance in his blog, showing his interest towards the group.
Both the song and the group have been very popular online, with the song topping M.Net's online chart and the group's name becoming a top search term. The group was also rewarded with three Cyworld Digital Music Awards, with both "Lollipop" and "Fire" winning "Song of the Month" awards and the group winning "Rookie of the Month" for May 2009. They received their first Mutizen award during their fourth stage performance in SBS Inkigayo (Popular Song) on June 14, 2009. They received their second Mutizen award on SBS Inkiagyo (Popular Song) on June 21, 2009. Along with their awards successes, 2NE1 signed a deal with Fila to become the new models for their commercial campaign 2 days after 2NE1's Mutizen win.
It was announced that 2NE1 would be heading over to the United States to work on their album, as Interscope Records chairman Jimmy Iovine showed interest in the group; however, they have no plans to debut in North America.
2NE1 is scheduled to participate in the 6th Asia Song Festival in September 2009, alongside Big Bang, Super Junior and Girls' Generation, to represent Korea; it was also reported that the group will be receiving this year's "Asian Newcomer's Award." 
2NE1 ended their promotions for their debut single "Fire" on June 28, 2009 in SBS Inkigayo.
On July 1, the group released the title of a song out of their first mini-album called "I Don't Care" online. "I Don't Care" is a reggae R&B ballad, co-produced by YG producers Teddy and Kush. After its digital release, interest in the song rose greatly, topping Cyworld's hourly music chart after an hour of its release. On July 9, they released a music video of "I Don't Care". Besides "I Don't Care", there are 4 other new songs featured on the mini album, "Let's go party", "In the club", "Stay Together", and "Pretty Boy", to form a total of 7 tracks.
On its first day, it recorded 50,000 sales in pre-orders. Their debut was a success on the Korean charts, as it heads straight to number 1 for its week - as it sold 13,675 albums. YG also stated that it already reached the 80,000 sales mark within 2 weeks which is impressive since 2NE1 is only a rookie. On August 2, 2009, 2NE1 performed a live remix version of "I Don't Care" at Popular Song. "I Don't Care" was also profiled in Perez Hilton's blog.. The group ended promotions for "I Don't Care" on August 30, 2009 in SBS Inkigayo with an unplugged version of the song. 2NE1 began promotion for "Pretty Boy" on September 6, 2009 with a performance at SBS Inkigayo and another performance at MusicBank on September 11, 2009. The group ended their promotions for their mini album on September 13, 2009 with a performance of "In the Club" at their good bye stage. They then performed Let's go party along with Fire, How Gee, Last Farewell (w/Big Bang) at the SBS Idol Big Show Chuseok Special. Their first full album is set to release in October 2009.
1st Full Album & Concert
On June 6, 2009, YG Entertainment reported that thoughts of releasing 2NE1's full album will be October or November 2009. This album will contain songs produced by Teddy, Kush and Big Bang member G-Dragon. The release of the album will be done after future promotions for "Pretty Boy", a song from their first mini-album, 2NE1. YG also stated there are thoughts of having the girls do an independent concert by the end of this year.. But it was confirmed that the group will have their first live concert at Araneta Coliseum, Philippines by January.
2NE1 was accused of plagiarism by Sony Music, as "I Don't Care" was alleged to sound similar to Lionel Richie's "Just Go". Sony Korea has denied 2NE1 the ability to promote the track any further without paying reparations. On September 21, 2009, Sisa Magazine, a news programme on MBC, stated that officials from Sony reportedly sent YG Entertainment warning letters about plagiarism. Sony's legal representative stated, "It was a hard decision for the music critics." However, they decided that there were similarities and accordingly issued a warning letter to the production company and composers. They have also denied YG Entertainment the permission to promote these songs. Their labelmates Big Bang and their member, G-Dragon are also under fire for plagiarism claims.