Formal planning for BART began with the setting up in 1957 of the Bay Area Rapid Transit District, a county-based special-purpose district body that governs the BART system. The district initially began with five members, all of which were projected to receive BART lines: Alameda County, Contra Costa County, the City and County of San Francisco, San Mateo County, and Marin County. Although invited to participate, Santa Clara County supervisors elected not to join BART due to their dissatisfaction that the peninsula line only stopped at Palo Alto initially, and that it interfered with suburban development in San Jose, preferring instead to concentrate on constructing freeways and expressways. Though the system expanded into Santa Clara County in 2020, it is still not a district member.