America had a fascination with the West. It represented cheap land, new opportunities, and a better life. Mountain men trapping beaver for fur companies later made a living guiding pioneers across the Lousiana Territory into Oregon Territory on the Pacific coast. Eventually, Britian and the United States signed a treaty establishing permanent boundaries between America and Canada. To the South, Americans poured into the Mexican state of Texas in search of cheap land. However, disputes with the Mexican government led to a rebellion and independence for Texas. James K. Polk became president in 1844 on a promise of westward expansion. He annexed Texas causing friction with Mexico that eventually led to war. By 1848, the United States had also annexed the Mexican territories of California and New Mexico. Finally, John Marshall's discovery of gold in the American River near Sacramento sparked a migration that swelled the population of California practically overnight.
After the Louisiana Purchase, Americans began moving into the West to make a better living. Some trapped beaver, some started farms, and others searched for gold.