It operates a fixed-route bus public transit service in the San Gabriel Valley region of eastern Los Angeles County, California, United States, as well as a rapid bus route to and from downtown Los Angeles from the El Monte Busway, and a few of its local routes reach the far northern and western edge cities of neighboring Orange and San Bernardino counties, respectively.

[13] In 1987, the Los Angeles County Transportation Commission (LACTC) approved Foothill to take over fourteen routes which serviced the San Gabriel Valley that were currently operated by SCRTD.

[6] Although service was planned to start on July 1, 1988,[14] the Foothill Transit Zone had been prevented from starting service in July by an injunction arising from a lawsuit filed by the drivers and mechanics unions (United Transportation and Amalgamated Transit Unions) of SCRTD against LACTC.

[12] Los Angeles Superior Court Judge Eli Chernow ruled that LACTC could not unilaterally transfer the lines without the consent of the SCRTD board of directors.

[11] SCRTD consented to Foothill Transit taking over the bus lines in December 1988 in return for the restoration of funding.

[12] Over the first five years, Foothill Transit consistently saved money compared to SCRTD's historical costs.

[19] Foothill executives made the service essentially strike-proof by insisting that two different companies operate the two bus yards, even if it would cost more in the short term.

[19] A representative of the union representing Metro's drivers, the United Transportation Union, accused Foothill of not paying its drivers a living wage; the president of the company that was then contracted to manage Foothill, William P. Forsythe, stated the US$20,000 (equivalent to $41,000 in 2023) typical annual pay of a Foothill driver "isn't bad for a service industry job" and admitted it wasn't fair "compared to MTA, but they've been overpaying for years.

The first strike against Foothill Transit started when Laidlaw drivers walked off in February 1996, asking for an immediate $1/hour raise and full medical coverage.

Teamsters Local 848 officials stated that drivers could not afford private health insurance, and had to rely on county services instead.

[21] The strike ended after thirteen days, when drivers accepted a 3% pay raise with no health coverage on a one-year contract under the threat they would be fired and replaced if they did not return to work.

[25] The last two lines operated by Metro (SCRTD's successor) in the eastern San Gabriel Valley were turned over to Foothill in 2016.

[26] In 2017, Foothill Transit hired two new contractors, Keolis and Transdev, both of which are French transportation companies, to manage both of their bus storage yards.

[27] On January 25, 2021, Foothill Transit received its first two all-electric double-decker buses, which were made by Alexander Dennis in the United Kingdom.

[40] Foothill Transit uses articulated New Flyer XN60 buses as well as two Double Decker Alexander Dennis Enviro500EVs for use on the Silver Streak (bus) line.