MAP ACTIVITYMap 27.1 The Interstate Highway System, 1930 and 1970 Built with federal funds authorized in the Interstate Highway and Defense System Act of 1956, superhighways soon crisscrossed the nation. Trucking, construction, gasoline, and travel were among the industries that prospered, but railroads suffered from the subsidized competition.READING THE MAP: What regions of the United States had main highways in 1930? What regions did not? How had the situation changed by 1970?CONNECTIONS: What impact did the growth of the interstate highway system have on migration patterns in the United States? What benefits did the new interstate highways bring to Americans and at what costs?