District 4 offices move to the State Building in San Francisco s Civic Center . The highway is dedicated in 1929. Posey Tube is commenced, to be completed in 1928. The bridge was privately built. The U. S. Highway numbering system is created.
Auto clubs take on the responsibility of making and placing route signs.
The first Dumbarton Bridge, on today s State route 84, opens. It spans San Francisco Bay between San Mateo and Alameda counties. The bridge was privately built. The first Carquinez Bridge, on today s Interstate 80, opens. It spans the Carquinez Strait between Contra Costa and Solano counties.