This PDF was downloaded from FHWA's Highway History website: https://www.fhwa.dot.gov/infrastructure/history.cfm.What follows is the documentation of the critical events during the building of the Interstate System. The record begins with the passage of the 1956 Highway Act, which kicked off the Interstate construction program. It ends in 1974 just after the passage of the 1973 Highway Act, which was landmark legislation for the Interstate System and the highway program in general