Sierra Entertainment, Inc. (formerly On-Line Systems and Sierra On-Line, Inc.) was an American video game developer and publisher. Founded in 1979 as On-Line Systems, by Ken and Roberta Williams, Sierra is known primarily for its graphic adventure game series such as King's Quest, Space Quest, Police Quest, Gabriel Knight, and Quest for Glory. Sierra On-Line was acquired by CUC International in February 1996 and became part of CUC International's newly established CUC Software (sold and renamed multiple times until becoming Vivendi Games in 2006). In June 2004, after months of significant downsizing and restructuring at the company, Sierra Entertainment was disestablished as a company in August that year. Sierra continued to operate as a division of Vivendi Games through June 2008, when Vivendi Games merged with Activision and formed Activision Blizzard, with Sierra becoming part of Activision Blizzard's Activision subsidiary, though shut down later that year. The "Sierra" brand name was revived by Activision in 2014 to re-release former Sierra games and some independently-developed games.