section_path: History/Westward expansion
section_name: Westward expansion
paragraph_text: Westward expansion
  
  By the late 18th century, Russia was established on the Pacific Northwest northern coastline, where it was engaged in maritime fur trade and was supported by various indigenous settlements in the region. As a result, the Spanish were showing more interest in controlling the trade on the Pacific coast and mapped most of its coastline. The first Spanish settlements were attempted in Alta California during that period. Numerous overland explorations associated with voyageurs, fur trade, and U.S. led expeditions, including the Lewis and Clark, Frémont and Wilkes expeditions, reached the Pacific.
  
  In 1803, during the presidency of Thomas Jefferson, the third U.S. president, Napoleon Bonaparte sold France's remaining North American territorial claims, which included regions west of the Mississippi River, to the U.S., in the Louisiana Purchase. Spain and the U.S. settled their western boundary dispute in 1819 in the Adams–Onís Treaty. Mexico fought a lengthy war for independence from Spain, winning it for Mexico (which included Central America at the time) in 1821. The U.S. sought further westward expansion and fought the Mexican–American War, gaining a vast territory that first Spain and then Mexico claimed but which they did not effectively control. Much of the area was in fact dominated by indigenous peoples, which did not recognize the claims of Spain, France, or the U.S. Russia sold its North American claims, which included the present-day U.S. state of Alaska, to the U.S. in 1867.