Construction began in the early 1960s. There were just three phases for the . The first phase, completed in 1967, ran from the San Joaquin County line to Los Banos. The second phase, completed in 1972, extended the freeway south to Wheeler Ridge and connected it to SR 99. The freeway then started to see traffic, as in Stockton there were only between the West Side Freeway and the Golden State Highway. The third phase, completed in 1979, extended the freeway to Sacramento and connected it to the northern I-5.