The United States began the 19th century as a new nation, little different from the original thirteen colonies along the east coast. Over the next hundred years, it vastly increased in size and population, and developed into the world’s largest agricultural and industrial economy. For most of this period, the U.S. focused on internal economic, political and social issues, but near the end of the century, it acquired overseas interests that involved it with international affairs.
In the first half of the century, the United States established itself as a viable nation and the dominant power in North America. The U.S. victory over the British in the War of 1812 firmly secured its independence. The Louisiana Purchase (1803) and victory in the Mexican American War (1846-48) expanded its territory across the continent. Protected by the Atlantic and Pacific Oceans, the U.S. avoided involvement in international politics. Through the Monroe Doctrine (1823), the U.S. claimed its status as the primary power in the Western Hemisphere while reaffirming its policy of remaining out of European affairs. During this period, the nation’s population grew rapidly, from 5 million in 1800 to 23 million by 1850.
