Interstate 680 (California) - Route Description

Route Description

The portion of this route from the Route 280/US101 junction to the Santa Clara/Alameda County line is named the Joseph P. Sinclair Freeway, after the District Engineer for District 4 Division of Highways (now Caltrans) from 1952 to 1964 pursuant to Assembly Concurrent Resolution 104, chapter 168 in 1967.

Between Alcosta Boulevard and the intersection with I-580, I-680 is officially named the "Officer John Paul Monego Memorial Freeway". It was named after Dublin Police Officer John Paul Monego, who died on December 12, 1998, in the line of duty at the age of 33 years, while responding to a takeover robbery. Named by Senate Concurrent Resolution 60, enrolled August 18, 2000.

From Route 24 to Route 4, the route is historically part of "El Camino Sierra" (The Road to the Mountains).

The portion of this route from about the Livorna Road interchange in Walnut Creek/Alamo to the Alcosta Blvd. interchange in San Ramon appears to be named the "Donald D. Doyle Highway". While serving in the California Assembly from 1953 to 1958, Donald D. Doyle co-authored the Short-Doyle Mental Health Act with California Senator Alan Short and authored legislation creating the ferry boat transportation system between Benicia and Martinez. The signs indicating this were erected in 1998.

Of the above names, only the name Sinclair Freeway for its designated portion usually appears on maps, and the other portions on maps are always unnamed, referred to as simply I-680.

The route begins at U.S. Route 101, where it acts as a continuation of Interstate 280 eastward. From here, it begins its journey northward through San Jose, where it meets the Capitol Expressway, signed as County Route G21. The next exit northbound is State Route 130, which is also known as Alum Rock Avenue. As it continues through Santa Clara County, it meets numerous local roads before interchanging with the Montague Expressway. Here, it exits San Jose and enters the city of Milpitas, California, where it meets State Route 237, often referred to as Calaveras Boulevard. After one more intersection, I-680 exits Santa Clara County and enters Alameda County.

In Alameda County, the freeway instantly begins in the city of Fremont, where it intersects State Route 262. Continuing through the city, it meets Mission Boulevard at State Route 238 before exiting the city. Amid Alameda County, it abruptly turns northeastward and enters a hilly area, where it crosses over Mission Pass, and descends into the Sunol Valley, where it joins State Route 84 for a short while. Afterwards, it enters Pleasanton and interchanges with Interstate 580. It enters Dublin for a short segment before exiting the county and entering Contra Costa County.

Upon entering Contra Costa County, the route meets numerous local roads through the cities of San Ramon, Danville, and Alamo before entering Walnut Creek, where it meets State Route 24. I-680 then enters Concord, where it meets State Route 242. Upon exiting Concord, it meets State Route 4. It then enters Martinez, where it follows the Benicia-Martinez Bridge over the Carquinez Strait, on which the route crosses the county line and enters Benicia in Solano County. In Benicia, I-680 interchanges with Interstate 780. It then exits the city and enters Fairfield, where it meets Interstate 80, where the route finds its north terminus.

In the wake of the September 11 Attacks, a U.S. flag was painted on a large piece of concrete on a hill along the Sunol Grade. It stayed there for nine years before Caltrans painted it over, as the mural had been painted on without authorization. Due to this action being taken shortly before July 4th, 2010, and also due to the mural's fame, this was met with controversy. The flag was replaced shortly later.