What legislative act focused on transportation as critical for economic affairs and national defense?

The Interstate Commerce Act of 1887 was the first federal law passed to regulate the railroad industry, which was seen as essential for both economic development and national defense. This act established the Interstate Commerce Commission (ICC), marking a significant shift in the way the federal government approached transportation. At the time, railroads were the primary means of transporting goods and people across long distances, and their efficient operation was crucial for the growth of the U.S. economy.

By focusing on regulating interstate commerce, the Act aimed to prevent monopolistic practices and ensure fair rates for the transport of goods, which would ultimately benefit the economy and facilitate trade. Additionally, a reliable and well-regulated transportation network was recognized as vital for national defense, as it would enable efficient mobilization of military resources in times of need.

In contrast, the other legislative acts mentioned focus on different aspects of labor relations and economic activity but do not specifically address transportation as a crucial element for economic affairs and national defense in the same historical context as the Interstate Commerce Act.