Why is the time period after the fall of the Western Roman Empire called the Dark Ages?

Why didn’t the portuguese have access to the territory that is present-day latin and north america

Why might the spanish government have approved of the encomienda system? a the system allowed for fair treatment of all under it, leading to a happy and prosperous colony. b the system used natives as slaves which meant the government was able to maximize their profit of exported goods. c the system allowed for mostly profitable trade within the different colonies. d the system was a great example of how to successfully run a colony, making spain a world power.

What mountains did the first transcontinental railroad cross