What Factors Contributed to American Expansion in the 1800s?

America’s steady westward expansion throughout the 19th century was influenced by a number of factors, among them a need for land for a burgeoning population, governmental policies which encouraged migrants west, and a sense of “manifest destiny” – the idea that Americans were destined by God to populate their entire country to the Pacific shore and beyond.

The swelling American population played a large part in the decision Americans made to head west. According to America’s second census in 1800, the U.S. population numbered 5.3 million. By the seventh census, in 1850, the population had quadrupled to 23.2 million. It’s been estimated that between 1820 and 1850, four million Americans moved west. In the first half of the 19th century especially, Americans were mainly farmers who needed arable land for their crops and livestock, land that was not available in the overcrowded and farmed-out east. There were, as well, financial panics (in 1818 and 1839) that uprooted people and sent them west seeking a fresh start.

The American government itself encouraged its citizens to move west, in large part by acquiring new territory from foreign powers. Thomas Jefferson’s 1803 Louisiana Purchase added 530,000,000 acres to America and the Lewis and Clark expedition of 1804-1806 revealed a land rich with promise for settlers. The United States aggressively continued it expansion by negotiating an 1846 agreement with Great Britain to cede the Oregon Territory (which included the present-day states of Oregon and Washington) to the United States. And the U.S. fought the Mexican-American War of 1846-47 in order to secure its hold on Texas and acquire California and much of the American southwest, opening these territories up to American settlers.

Some American citizens and government officials believed in the notion of “manifest destiny,” a term coined by journalist John L. O’Sullivan in 1845, which meant Americans were destined to control all the continental lands west to the Pacific, south to the Rio Grande, and north to Canada. But manifest destiny could also be a guise for opportunism. America’s expansion west was an expansion for merchants as well as farmers. California was known for its fertile land and, later, its rich gold fields, but American merchants wanted to acquire it for its Pacific ports. These allowed for American expansion into the Pacific Ocean for trade with China and Japan; eventually, the U.S. established a powerful American naval base in Hawaii.

Factors that contributed to America’s westward expansion in the later half of the 19th century included the quelling of Native American resistance and relocation of tribes to reservations, gold rushes (in Colorado, California, and the Black Hills of South Dakota) and the building of the Intercontinental Railroad. By the Spanish-American War of 1898, having reached its borders, America was now ready to turn its expansionist ambitions abroad.