| Term | Definition |
| James K. Polk | 11th President, led US to war with Mexico |
| Zachary Taylor | American general in war with Mexico and 12th President |
| Stephen Kearny | American general in war with Mexico, he captured Santa Fe without firing a shot, captures Sante Fe, secures California. "Long Marcher" |
| Republic of California | the nation proclaimed by American settlers in California when they declared their independence from Mexico, 1846 |
| Winfield Scott | American General who along with Zachary Taylor, attacked Mexico during the Mexican War |
| Treaty of Guadalupe Hidalgo | the 1848 treaty ending the US war with Mexico, in which Mexico ceded California and New Mexico to the US |
| Gadsden Purchase | an 1853 purchase by the US of land from Mexico, establishing the present US- Mexico boundary |
| forty-niners | one of the people who migrated to California in search of riches after gold was discovered there in 1848 |
| gold rush | a movement of many people to a region in which gold has been discovered |