Expansion West: From the Mississippi to the Pacific, 1789-1850

The new United States was hungry for land from the start. The belief that America was destined to expand westward drove policy for the entire 19th century.

The Louisiana Purchase, 1803:

President Thomas Jefferson's greatest achievement was a real estate deal. In 1803, Napoleon Bonaparte, facing war with Britain and needing cash, offered to sell the entire Louisiana Territory — roughly the central third of modern America, 828,000 square miles — for just $15 million. Jefferson, a strict constitutionalist who was unsure whether a president had the authority to make such a purchase, nevertheless agreed immediately. The Louisiana Purchase doubled the size of the United States overnight.

To understand what they had bought, Jefferson sent Meriwether Lewis and William Clark on a two-year expedition (1804-1806) to map the territory, make contact with Native peoples, and record the natural environment. They returned with journals that fired American imaginations about the West.

Indian Removal Act, 1830:

As American settlers pushed westward, they increasingly coveted the fertile lands of the Five Civilised Tribes — the Cherokee, Chickasaw, Choctaw, Creek, and Seminole — who lived in the southeastern states. President Andrew Jackson, a frontier soldier with deep contempt for Native rights, pushed through the Indian Removal Act in 1830. It gave the president power to negotiate treaties forcing eastern tribes to relocate west of the Mississippi, to the "permanent Indian frontier."

The Cherokee of Georgia resisted legally. Their case went to the Supreme Court, which ruled in their favour (Worcester v. Georgia, 1832). Jackson reportedly responded: "John Marshall has made his decision; now let him enforce it." In 1838, US Army troops forcibly removed approximately 17,000 Cherokee westward during the winter months. Over 4,000 died from cold, disease, and exhaustion on what the Cherokee called "Nunna daul Tsuny" — "The Trail Where They Cried" (the Trail of Tears).

Manifest Destiny:

In 1845, journalist John O'Sullivan coined the phrase "Manifest Destiny" — the belief that it was God's plan for Americans to expand across the entire continent. This was not merely propaganda; millions genuinely believed it. Manifest Destiny provided moral justification for displacing Native peoples, annexing Texas (Republic of Texas declared independence from Mexico in 1836, joined the US in 1845), and the war with Mexico.

The Mexican-American War, 1846-1848:

President James Polk manufactured a border incident to trigger war with Mexico. American forces swept through New Mexico and California. The Treaty of Guadalupe Hidalgo (1848) forced Mexico to cede over 500,000 square miles — modern California, Nevada, Utah, Arizona, New Mexico, and parts of Colorado and Wyoming — in exchange for $18 million. The US had reached the Pacific.