The National Interstate and Defense Highways Act was enacted in 1956 to create a network of highways across the United States. This legislation aimed to improve transportation efficiency and enhance national defense by facilitating the movement of military personnel and equipment. The act authorized the construction of over 41,000 miles of interstate highways, significantly transforming American travel and commerce. Funded by a federal gas tax, the act also aimed to promote economic growth by connecting urban and rural areas. The interstate system has since become a vital part of American infrastructure, influencing the development of cities and suburbs throughout the country.