Here I-580 turns southeast to a junction with I-5, paralleling the California Aqueduct and Delta–Mendota Canal along the foothills, while I-205 continues east as a six-lane roadway, immediately crossing both waterways.

I-205 also serves to connect the Bay Area with popular weekend destinations such as Yosemite National Park, Reno, and Lake Tahoe.

[9] San Joaquin County paved the portion near Tracy with asphalt with their own bond issue, passed in 1909, and the state later resurfaced it with concrete.

[15] In 1926, the American Association of State Highway Officials designated the Stockton–Bay Area route as US 48,[16] which was absorbed by an extension of US 50 by the early 1930s.

[23] During early planning for the Interstate Highway System, the main north–south route through California[24] (now I-5) was to use SR 99 through the San Joaquin Valley; a connection to the Bay Area split near Modesto and roughly followed US 50.

[25] The Bureau of Public Roads approved a move to the proposed Westside Freeway in May 1957, and, in November, they added a North Tracy Bypass that would connect I-5 and I-580.

[26] Construction began in the late 1960s,[27][28] incorporating part of the 1954 expressway and a new alignment bypassing Tracy to the north, and the $14-million (equivalent to $84.8 million in 2023[29]) road opened to traffic on December 21, 1970.

[30] (A short piece at the west end, including the bridge over the California Aqueduct, was upgraded several years earlier when I-580 and I-5 to the south were built.

in 1999[32] and converting two diamond interchanges to partial cloverleafs—Grant Line Road in about 1997[31] and Mountain House Parkway in 2007 (including ramp meters).