The Eastern Contra Costa Transit Authority (ECCTA) JPA was formed in 1976 by the cities of Antioch, Brentwood, and Pittsburg, along with the County of Contra Costa. When Oakley was incorporated in 1999, the JPA was amended to admit Oakley on April 1, 2001. Tri Delta Transit fixed route service began on June 6, 1977, celebrated by an inaugural bus starting from Antioch City Hall (10 a.m.), traveling to Oakley (10:30), Brentwood City Hall (11), Pittsburg, and ending in
West Pittsburg (2 p.m.). For the first week, free rides were offered. Initial service was provided for two local routes in Antioch and Pittsburg, which connected with express bus service serving BART.
AC Transit operated the service under contract until 1984, when it was transferred to a private operator, and ECCTA acquired its first buses; prior to that, AC Transit owned the buses it used for Tri Delta Transit. Some of the buses used in 1978 included 29-foot models, shortened from 35-foot buses at the AC Transit shops.
Dial-a-ride on-demand transit services have been provided since 1979 using contracted private operators. ECCTA consolidated fixed route and on-demand services with a single operator when the contract with AC Transit was discontinued in 1984. In 1986,
Laidlaw Transit, Inc. (later
First Transit, now
Transdev) begin operating Tri Delta Transit. The ECCTA headquarters in Antioch was built in 1987, consolidating administration, operations, and maintenance at a single facility; expansions in 2004 provided additional space and bus parking. ==Overview of fixed-route service==