How did the united states complete westward expansion?

In 1803 the Louisiana Purchase took place, doubling the size of the country. By 1840 almost 7 million Americans had migrated westward in hopes of securing land and being prosperous. The belief that settlers were destined to expand to the west is often referred to as Manifest Destiny.

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answer: c

explanation: i have done that passage before

of what agreement it does not show