The significance of the Interstate Highway Act, enacted in 1956, in U.S. history lies in its transformative impact on transportation, economy, and suburban development. This act authorized the construction of a vast network of highways connecting major cities, facilitating the movement of goods and individuals across the nation. It significantly contributed to the rise of the automobile culture and suburbanization, as people increasingly moved away from urban centers. Furthermore, the Interstate Highway System boosted commerce, contributed to the growth of the national economy, and reshaped the landscape of American society throughout the late 20th century.