Much of Alvarado Canyon Road from San Diego to La Mesa was originally built between 1947 and 1950, a bypass of the old US 80 routing along El Cajon Boulevard and La Mesa Boulevard. Work began to convert the original US 80 divided highway into a freeway in 1960, and the freeway was complete west of El Cajon by April 1962. Priority was given to planning US 80 in 1962 by the California Chamber of Commerce. In 1964, I-8 was officially designated by the California State Legislature, and the US 80 designation was removed. By 1965, I-8 from Fairmount Avenue to El Cajon Boulevard was one of the first freeway stretches in the county to have a center barrier installed in the median.