The Territory Expansion

     When the United States won its independence, the Treaty of Paris  of 1783 defined the national boundary asbeing to the east of the Mississippi River. The US government shifted their attention on the city New Orleans, as whoever controlled New Orleans（新奥尔良） actually controlled trade on the Mississippi River. So by taking advantage of the war in Europe, President Thomas Jefferson made France agree to sell Louisiana Territory for $15 million. This was a vast region more than 2.6 million km², stretching from the Great Lakes to the Gulf of Mexico.The Louisiana Purchase doubled the size of the country and opened the door for America’s westward expansion.

     In 1819, the US “purchased” Florida (about150,000 km²in size) from Spain after having occupied it for several years.

     In 1845, the United States annexed（合并） the Mexican territory of Texas. Before that, the US settlers had already formed an “independent government” with Washington’s support. Further provocations（挑衅） of soldiers on the border resulted in the Mexican-US War of 1846-1848. The UnitedStates added to itself a territory of 2.45 million km², embracing the present state of Texas, California, Arizona, Nevada, Utah, New Mexico, Colorado, andpart of Wyoming. In the same year, the United States also force Great Britain to cede（割让） the Oregon Region.

     In 1867, the United States purchased from Czarist Russia（沙皇俄国） the territory of Alaska and the Aleutian Island for $7.2million. This territory is twice as large as the original 13 colonies.

      By annexation, purchase and war, the United State rapidly pushed the national border to the Pacific Ocean. By the mid-19th century, its national territory had reached over 9 million km², about 10 times the size of the original 13 colonies.

Indian Removal

    In 1830 with the encouragement of PresidentAndrew Jackson, Congress passed a law called the Indian Removal Act. It required the Indians living east of the Mississippi River should move to IndianTerritory west of the river. This territory later became part of the state of Oklahoma.

    In the next two decades, many Native American tribes were forced to remove from southeast and relocate fartherwest.  During 1838, the Cherokees（切罗基人）, one ofthe five major Native American nations, were made to leave their homelands in Tennessee, Alabama, North Carolina, and Georgia and marched more than 1,600 kmto their new home Oklahoma. An estimated 4,000 of the 15,000 Cherokees died during this forced migration. This tragic became known as the “Trail of Tears.”

The Gold Rush（淘金热） of 1849    

    Purchases and treaty agreements, along with victory in war with Mexico, expanded the US from the Atlantic to the Pacific.After gaining control over the West, Americans began moving into these lands in ever increasing numbers.

    One event that drew people to the West was the discovery of gold in California. Gold fever brought a huge wave of people into the West. In 1849, over 80,000 people traveled west to the California gold fields. Although many newcomers returned home after the uproar died down,enough people stayed to establish California as a state just two years after the gold rush began. More than $1 billion in gold was mined there. This money helped build railroads and factories, establishing United States as a nation of industry.