 The expansion of American railroads peaked in the 1910s and during the Great Depression many railroads suffered financial difficulties which led to some railroad bankruptcies.World War II caused a surge in the use of California's railroads but with the government funded construction of the Interstate Highway System in the 1950s and the expansion of the U.S. airline industry passenger rail service declined dramatically.The 1970s saw the end of private passenger railroads in California, the creation of a national passenger railroad (Amtrak) and the Bay Area's opening of the BART rail-system.