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Thomas Jefferson is inaugurated as the third president in Washington, DC.
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United States signs treaty and agrees to pay France $15 million for the Louisiana Territory, which extends west from the Mississippi River to the Rocky Mountains and comprises about 830,000 sq mi.
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Lewis and Clark set out from St. Louis, Mo., on expedition to explore the West and find a route to the Pacific Ocean.
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U.S. declares war on Britain over British interference with American maritime shipping and westward expansion.
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James Monroe is inaugurated as the fifth president.
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In an effort to maintain the balance between free and slave states, Maine (formerly part of Massachusetts) is admitted as a free state so that Missouri can be admitted as a slave state; except for Missouri, slavery is prohibited in the Louisiana Purchase lands north of latitude 36°30'
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Continental Congress adopts the Articles of Confederation, the first U.S. constitution.
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Samuel Colt invented the first revolver.
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Harriet Tubman escapes from slavery and becomes one of the most effective and celebrated members of the Underground Railroad.
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Alexander Graham Bell patents the telephone.