Foothill Transit, a joint powers authority of 21-member cities in the San Gabriel and Pomona Valleys, was created in 1988 after the former Southern California Rapid Transit District (RTD) announced service cuts and fare increases that would negatively impact the San Gabriel Valley. In an effort to provide better bus service to the community while reducing costs and improving local control, the Los Angeles County Transportation Commission (LACTC) approved Foothill Transit's application to assume operation of 14 lines which were operated by RTD.

Foothill Transit now operates 35 fixed-route local, express and rail-feeder lines, covers 327 square miles, and serves 16 million customers each year, making it the second-largest fixed route public transit provider in Southern California. This number is up from 9.5 million boardings at the time of Foothill Transit's original application.
In 2002, Foothill Transit entered a cleaner new era by beginning its conversion to a compressed natural gas (CNG) fleet. Foothill Transit has put into service 117 CNG buses and is planning to have an all-CNG fleet by 2011. The agency also opened its second operations and maintenance facility in October 2002. Located in Irwindale/Arcadia, it joined Foothill Transit’s first agency-owned facility in Pomona, which opened in 1997. Prior to the opening of these facilities, the agency had to rely on its operations contractors to provide their own facilities.