westward expansion By jafi7397 Oct 1, 1782 The United States Oct 1, 1803 Louisiana Purchase Oct 1, 1813 West Florida Annexation Oct 1, 1819 Red River Cession Dec 1, 1819 East Florida Oct 1, 1842 Webster Ashburton Treaty Oct 1, 1845 Texas Annexation Oct 1, 1846 Oregon Territory Oct 1, 1848 Mexican Cession Oct 1, 1853 Gadsden Purchase