United States contains the administrative territorial entity Oregon
In the late 18th century, American settlers began to expand further westward, some of them with a sense of manifest destiny. The 1803 Louisiana Purchase almost doubled the nation's area, Spain ceded Florida and other Gulf Coast territory in 1819, the Republic of Texas was annexed in 1845 during a period of expansionism, and the 1846 Oregon Treaty with Britain led to U.S. control of the present-day American Northwest.As it expanded further into land inhabited by Native Americans, the federal government often applied policies of Indian removal or assimilation. The Trail of Tears in the 1830s exemplified the Indian removal policy that forcibly resettled Indians. The displacement prompted a long series of American Indian Wars west of the Mississippi River and eventually conflict with Mexico. Most of these conflicts ended with the cession of Native American territory and their confinement to Indian reservations. Victory in the Mexican–American War resulted in the 1848 Mexican Cession of California and much of the present-day American Southwest, with the U.S. now spanning the continent. The California Gold Rush of 1848–1849 spurred migration to the Pacific coast, which led to the California Genocide and the creation of additional western states.US expansion increased acreage under mechanical cultivation and increased surpluses for international markets. Economic development was spurred by giving vast quantities of land, nearly 10% of the total area of the United States, to white European settlers as part of the Homestead Acts, as well as making land grants to private railroad companies and colleges. Prior to the Civil War, the prohibition or expansion of slavery into these territories exacerbated tensions over the debate around abolitionism.
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