The Great Depression of the 1930s affected Michigan more severely than many other places because of its industrial base. However, the state recovered in the post World War II years. The Mackinac Bridge connecting the Upper and Lower Peninsulas was completed and opened in 1957. By the 1960s, racial tensions produced unrest through the nation, and Detroit experienced a dramatic instance with the 12th Street Riot in 1967. By the 1980s, the state saw a decline in automobile sales and unemployment climbed. Michigan continues to diversify its economy away from its dependence on the automobile industry.