What was the MOST important or historically significant effect (result) of U. S. growth and expansion during the late 19th century? Why?

The massive increase in the economy

Explanation: The expansion influenced more trade in foreign countries. Economic reasons industrialization in the late 1800s increased the need to trade with other countries.

(d) rivers.

explanation:

civilizations developed around rivers because their waters provided places to hunt and fish. also, as the rivers flooded, the lands around them became fertile. this allowed them to support farming. this is especially true of the nile river, which flooded the same time each year.

a.

congress passed laws allowing for free passage between states.