One of the most amazing engineering buildings in the United States is the San Francisco-Oakland Bay Bridge. The American Society of Civil Engineers designated the bridge as a nationally significant structure in terms of engineering as well as its significance in California and national transportation history. The bridge is also one of the oldest continuously operating suspension bridges in the world. It connects Oakland and Yerba Buena Island, forming an uninterrupted link between San Francisco and Berkeley. It is also the only bridge that crosses over the bay between San Francisco and Marin County. Opened in April 1937, it was built by McGolrick Park & Company, Inc., who had previously constructed the Lincoln and Golden Gate Bridges. The main span measures 1,070 feet from end to end, making it the longest continuous truss bridge in the world at the time it was built. The bridge's importance cannot be overstated: It is one of the major connectors between Northern and Southern California, providing a vital connection between the metropolitan areas on either side of the bay. It also serves as a major roadway across the bay for traffic entering or leaving San Francisco. There are no tunnels under the bay, so all traffic has to cross it some how. Ships can't go around the city because of the bridges, so they must use the water approach if they want to enter or leave the port area.