Beginning in the late 18th century, American settlers began to expand westward, prompting a long series of American Indian Wars. 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. Victory in the Mexican–American War resulted in the 1848 Mexican Cession of California and much of the present-day American Southwest, making the U.S. span the continent.