In 1966, Chi Delphia was formed as a little sister program to Delta Chi Fraternity at Cal State-Sacramento. In 2001, after changing its name to Chi Delta, the organization established a chapter at Sonoma State. The campus opened for extension in 2007 and Alpha Delta Pi was selected to affiliate with the members of Chi Delta, forming the sorority's 12th California chapter. That spring, 31 Chi Delta women went through the Alpha Ceremony, and in August, 49 new members joined through the colony recruitment process. As a colony, they helped decorate the Ronald McDonald House for the holidays and made cookies. They were the first Greek organization to pair with the Cotati Community Center for an event for 200 local children. They held leadership positions in Associated Students and JUMP, a campus service organization. In November, at the chapter's installation, seven Chi Delta alumnae were initiated along with 79 Alpha members.