State Route 24 (SR 24) in the U.S. state of California is a heavily traveled east–west freeway in the eastern side of the San Francisco Bay Area of northern California that runs from the Interstate 580/Interstate 980 interchange (just east of the MacArthur Maze) in Oakland, and through the Caldecott Tunnel under the Berkeley Hills, to the Interstate 680 junction in Walnut Creek. It lies in Alameda County, where it is highly urban, and Contra Costa County, where it passes through wooded hillsides and suburbs.