westward expansion By alliii Apr 30, 1803 Louisiana Purchase Treaty was dated May 2, 1803 Louisiana Purchase Treaty was signed Jan 1, 1811 Begining of Oregon Trail Feb 22, 1819 U.S. acquires Florida from Spanish Dec 31, 1840 End of Oregon Traill Apr 12, 1844 Texas Annexation signed Mar 1, 1845 Texas became the 28th state People involved: John Tyler James K. Polk Apr 25, 1846 Mexican - American War Began Feb 2, 1848 Mexican - American War Ended Mar 10, 1849 Mexican Cession ratified Dec 30, 1853 Gadsden Purchase