J. G. Brill Company
The trolleybus system's original fleet, owned and operated by the Market Street Railway when only MSRy was operating trolleybuses in San Francisco, were built by the J. G. Brill Company. MSRy merged with Muni in 1944, and in the years since then the trolleybus fleet has also included vehicles built by the St. Louis Car Company, Marmon-Herrington, Twin Coach, and Flyer Industries.