The leaders of the country who were elected president during the Westward Expansion Era were John Tyler, James Polk and Zachary Taylor.

President John Tyler and the Westward Expansion Era: John Tyler Presidency (1841-1845)
Important events in United States History during the presidency of John Tyler includes the Treaty of 1842 with Great Britain, First telegraph line, 1844 and The Oregon Trail - United States History for Kids.

President James Polk and the Westward Expansion Era: James Polk Presidency (1845-1849)
Important events in United States History during the presidency of James Knox Polk includes the Manifest Destiny, The Mexican-American War, The California Republic and the Bear Flag Revolt, Oregon Treaty 1846, California Gold Rush, 1848 and the Treaty of Guadalupe Hidalgo - United States History for Kids.

President Zachary Taylor and the Westward Expansion Era: Zachary Taylor Presidency (1849-1850)
Important events in United States History during the presidency of Zachary Taylor includes the Galphin scandal - United States History for Kids.

Crash Course in American History: Summaries of Events in the Westward Expansion Era
A fast overview, or crash course in American History, during the Westward Expansion Era can be obtained from the interesting and important articles on United States History for Kids that can be found in the section. There are summaries and definitions of the key historical events for each of the presidencies of the Westward Expansion Era from 1841 - 1850.