Today, the Caldecott Tunnel connects Alameda and Contra Costa Counties, located in the San Francisco Bay Area. The original two bores of this tunnel opened in 1937, the same year as the San Francisco-Oakland Bay Bridge, and changed Contra Costa County from an area of small rural communities into one of growing suburbs. But this was not the first tunnel to connect these counties. The Kennedy Tunnel, opened in 1903, was accessed by steep and winding roads and located several hundred feet above todays tunnel. A third bore of the Caldecott Tunnel was opened in 1964 and a long-awaited fourth bore...