Final answer:
The development of the federal highway system, including Route 66 and the Interstate, played a crucial role in American economic growth, cultural shifts, and national connectivity, while the Federal Highway Act of 1956 drastically improved cross-country travel.
Step-by-step explanation:
The importance of road construction and its impact on American history is evident through key developments such as the federal highway system, the construction of Route 66, and the Interstate Highway System initiated under Eisenhower's presidency. These advancements in transportation infrastructure facilitated economic growth and had profound effects on culture, business, urban development, and the overall connectivity of the nation. The Federal Highway Act of 1956 is particularly noteworthy for its significant influence on private and commercial transportation, despite concerns about its impact on small towns and existing commercial centers.