Which of the events listed had most affected the early development of the United States? Why do you think so? What were the effects of the event? A. The War of 1812
B. The Louisiana Purchase
C. The Monroe Doctrine

I would say B.. The Louisiana Purchase

Explanation:

Because of this, Americans traveled to this area to explore and in hopes to find riches. This also made the United States a larger country and encouraged people to travel to this new area. After the area was bought, more land was explored and found.

disease was the number one killer of native peoples. they had had little exposure to the diseases of europe. this led to some villages being almost completely wiped out and some tribes destroyed.