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Lesson 3 of 84 · Westward Expansion
Lewis and Clark: Exploring the West
Secondary sources — textbooks, documentaries, encyclopedia articles — are created after an event. They analyze and interpret primary evidence to build a broader understanding.
Key Facts
1
Historians use evidence to support claims.
2
Timelines show events in order.
3
Cause and effect explain why things happen.
Check Your Understanding
Question 1
1 of 2Why do we study history?