Final answer:
The Transcontinental Railroad most likely resulted in the expansion of interstate commerce nationwide by connecting various regions, enhancing transportation, and fostering urbanization.
Step-by-step explanation:
The economic impact most likely resulting from the map of the Transcontinental Railroad was b) Expanding interstate commerce nationwide. The construction of the railroad significantly reduced the cost and time of transportation, connected various parts of the country, and facilitated the movement of goods and people. This immense transportation improvement allowed for the growth of a national market system and a surge in interstate commerce. Moreover, the Transcontinental Railroad led to urbanization, as it made access to urban centers easier for people and goods. It didn't eliminate overseas trade with Europe, nor did it decrease the influence of big business; in fact, it enhanced big business influence by providing larger markets and distribution networks. It also did not directly lead to the rapid rebuilding of the South after the Civil War; reconstruction was a complex process influenced by many other factors.