What development in the 1950s significantly increased economic activity that continues today?

The interstate highway system, established in the 1950s, profoundly impacted economic activity and continues to do so today. This extensive network of highways facilitated efficient transportation across the United States, enabling the movement of goods and services over long distances quickly and effectively.

By connecting urban centers with rural areas, the system helped stimulate commerce, allowing businesses to reach broader markets. It also had a significant effect on the trucking industry, which became a primary mode of cargo transport, thus enhancing supply chain operations and logistics. Additionally, the interstate system contributed to the growth of suburbs, as people could live further away from their workplaces, thus transforming social structures and patterns of living.

This infrastructural advancement laid the groundwork for modern economies, influencing trade practices, urban development, and regional economics that continue to be relevant today. Other options, while important, do not match the foundational role the interstate highway system played in reshaping economic landscapes in the post-World War II era.