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President Thomas Jefferson buys the Louisiana Territory from France for $15 million. This doubles the size of the United States and provides a large area to the west of the country for expansion.
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Explorers Lewis and Clark map out areas of the Louisiana Purchase and eventually reach the Pacific Ocean.
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Missouri asks to be admitted into the Union. This application causes a nationwide dispute between slavery and antislavery sympathizers which is not settled until 1820 with the Missouri Compromise. There are 10,000 slaves in Missouri.
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Congress passes the Missouri Compromise, a bill that temporarily resolves the first serious political clash between slavery and antislavery interests in U.S. history.
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President James Monroe allows Missouri to enter the country as a slave state, and Maine is allowed to enter the country as a free state.
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Congress passes a law to move Native Americans from the Southeast to the west of the Mississippi River.
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The Cherokee Nation is forced to march from the east coast to Oklahoma. Many thousands die along the way.
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People begin to travel west in wagon trains on the Oregon Trail. Around 300,000 people would take the trail over the next 20 years.
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England signs the Oregon Treaty handing over the Oregon Territory to the United States.
