Answer:
first wave of industrialization
Explanation:
through the construction of the Transcontinental Railroad, which facilitated the transportation of goods across the nation.
It is absolute (sorry if the answer is wrong)
Well, once the Americas were discovered and the colonist found that the soil was agreeable to grow different crops such as tobacco and cotton the colonists realized that they needed people to pick the crops. Originally indentured servants did the hard labor but then when they found that they could get labor by trading goods with African tribal leaders they resorted to importing Africans to the Americas as labor. The tribes in Africa were constantly fighting and whichever side won the losers became the slaves of the winning tribe. However, as Europeans brought valuable things to the continent of Africa such as weapons, salt, gold, and other things the leaders of the winning tribe would give their slaves to the Europeans. There were cases when Blacks captured other Blacks in Africa for the sole purpose of giving them to the European traders. Hopefully this helps. If you haven't see the movie La Amistad, it will explain in more detail what I have written. I learned a lot from that movie. I must warn you the first 5 to 10 minutes are a bit gory. I had a hard time watching that part.
Well one reason is that it was to divide Berlin from 1961 to 1989.
Hope I Helped!