Westward Expansion: The U.S. Growth to the Pacific Ocean
The process is called Westward Expansion (or Manifest Destiny—the ideological framework).
Key Milestones (19th Century)
- 1803: Louisiana Purchase (828,000 mi² from France).
- 1818/1846: Oregon Treaty (49th parallel) with Britain.
- 1819: Adams-Onís Treaty (Florida from Spain).
- 1845: Texas Annexation.
- 1846–1848: Mexican–American War → Mexican Cession (CA, NV, UT, AZ, NM, CO).
- 1848: Gold Rush (CA) accelerates settlement.
- 1869: Transcontinental Railroad completed (Promontory, UT).
- 1890: Census declares frontier "closed."
Mechanisms
- Treaties, purchases, wars, legislation (Homestead Act 1862), trails (Oregon, California, Santa Fe), railroads, mining, ranching, farming.
Consequences
- Indigenous displacement, wars, reservations, cultural devastation.
- Environmental transformation (plains, forests, rivers, species).
- Sectional conflict over slavery → Civil War.
- Continental nation-state realized.
Westward Expansion reshaped North America's demography, ecology, politics, and identity.
Wanderlust World