Linkin Park is an American rock band from Agoura Hills, California. Formed in 1996, the band rose to international fame with their debut album Hybrid Theory (2000), which was certified Diamond by the RIAA in 2005 and multi-Platinum in several other countries. Their following studio album Meteora continued the band's success, topping the Billboard 200 album chart in 2003, and was followed by extensive touring and charity work. Having adapted nu metal and rap metal to a radio-friendly yet densely layered style in Hybrid Theory and Meteora, the band explored other genres on their next studio album, Minutes to Midnight (2007).

Linkin Park has sold more than 70 million records. The group's first studio album Hybrid Theory is one of the best-selling albums in the US (10 million copies shipped) and worldwide (27 million copies sold). Billboard estimates that Linkin Park earned US$5 million between May 2011 and May 2012, making them the 40th-highest-paid musical artist. 11 of the band's singles have reached the number one position on Billboard's Alternative Songs chart, the second-most for any artist.  In 2003, MTV2 named Linkin Park the sixth-greatest band of the music video era and the third-best of the new millennium. Billboard ranked Linkin Park No. 19 on the Best Artists of the Decade chart. The band was recently voted as the greatest artist of the 2000s in a Bracket Madness poll on VH1. In 2014, the band was declared as the Biggest Rock Band in the World Right Now by Kerrang!. In 2015, Kerrang! gave "In the End" and "Final Masquerade" the top two positions on Kerrang!'s Rock 100 list.  Linkin Park became the first rock band to achieve more than one billion YouTube hits. Linkin Park also became the fifteenth most liked page on Facebook, tenth most liked artist, and most liked group followed by the Black Eyed Peas. Linkin Park's "Numb" is the third and "In the End" is the sixth "timeless song" on Spotify. The two songs making Linkin Park the only artist to have two timeless songs in top ten.  Hybrid Theory by the group is listed in the book 1001 Albums You Must Hear Before You Die, It was also ranked at #11 on Billboard's Hot 200 Albums of the Decade. In addition the album was included in Best of 2001 by Record Collector, The top 150 Albums of the Generation by Rock Sound and 50 Best Rock Albums of the 2000's by Kerrang!. The album Meteora was included in Top 200 Albums of the Decade by Billboard at #36. The album sold 20 million copies worldwide. The collaborated EP Collision Course with Jay-Z, became the second ever EP to top the Billboard 200, going on to sell over 300,000 copies in its first week after Alice in Chains' Jar of Flies in 1994. The album Minutes to Midnight in the United States, the album had the biggest first week sales of 2007 at the time, with 625,000 albums sold. In Canada, the album sold over 50,000 copies in its first week and debuted at number one on the Canadian Albums Chart. Worldwide, the album shipped over 3.3 million copies in its first four weeks of release.  The New York Times' Jon Caramanica commented Linkin Park "brought the collision of hard rock and hip-hop to its commercial and aesthetic peak" at the beginning of the 2000s. Several rock and non-rock artists have cited Linkin Park as an influence, including Proyecto Eskhata, Of Mice & Men, One Ok Rock, Bishop Nehru, Misono, From Ashes to New, Bring Me the Horizon, Red, Girl on Fire, Manafest, Silento, 3OH!3, The Prom Kings, AJ Tracey, Kiiara, The Chainsmokers, Kevin Rudolf, blackbear, Tokio Hotel, and Stormzy.

Using a quote from the above article, answer the following question: What was their best selling album?
The group's first studio album Hybrid Theory is one of the best-selling albums in the US