Turtle Rock Studios was officially founded in 2002. The team of about six people had limited resources so set up work space in Booth’s garage. The name “Turtle Rock” derived from the name of a neighbourhood where Booth lived. The team eventually expanded the studio and rented an office, and continued the development of Condition Zero. The game was officially released in 2004. Satisfied with the work done by Turtle Rock, Valve continued to contract them to work on the Xbox version of Counter-Strike, as well as the next installment of the series, Counter-Strike: Source, and Half-Life 2: Deathmatch. Upon the release of Source, the company wanted to work on a new game, and gained support from Valve. The team later chose to design a first-person wizard combat game.
After that, the team decided to remove all the Counter-Strike content and started developing the zombie game, in which players have to plant zombie bait and kill all the zombies present in the level. The focus later shifted to evacuating and surviving in a zombie-infested area. The project was later presented to Valve, which helped the game’s funding and publishing. The project’s name was Left 4 Dead, and its development began in 2005. The title was officially announced on November 20, 2006, and was released in November 2008 for Microsoft Windows and the Xbox 360.
On January 10, 2008, before the release of Left 4 Dead, Valve Corporation announced that it had purchased Turtle Rock in an effort to expand the company’s console market. Gabe Newell, founder and president of Valve Corporation, added that it was an easy decision for the company to make, as they had high expectations for Left 4 Dead and considered themselves having a long-term relationship with Turtle Rock. After being acquired by Valve, Turtle Rock served as Valve’s in-house satellite development team, and was renamed Valve South.