Some important things about the American history The North American Continent Has Been Populated for Over 15,000 Years And the Columbus Discovered the Americas in 1442. Also some important events in the American history Civil War and Reconstruction, 1861-1877 and the The American Revolution, 1763 - 1783. one of the most important piece of the American history the Declaration of Independence, 1776 because Perhaps the most well-known document in American history, the Declaration of Independence was completed on July 4, 1776.