The Mexican-American War and Mexican Cession Manifest Destiny (the belief that it is America’s obvious fate to spread west) Cause #1 began to sweep the nation in the 1840s as thousands of Americans took to the trails leading westward- Oregon Fever When Democrat President James K. Polk won the Election of 1844, Texas and Oregon were soon annexed as U.S. territories- Cause #2 * Tensions between Mexico and the U.S increased, especially over the border issue (Nueces or Rio Grande?)- Cause #3

* When Mexico refused to meet with U.S. diplomat John Slidell and turned down the $30 million offer for California and New Mexico, going to war was just a matter of time- Cause #4 * General Zachary Taylor’s men were fired upon at the Rio Grande near the disputed border, and the war began (1846)- Cause #3 continued… * Whigs and Abolitionists opposed the war * The Bear Flag Revolt also began in 1846 in California

* The war was over in a year, and Mexico had lost all of its land including Mexico City * The Treaty of Guadalupe Hidalgo forced Mexico to give up its northern territory stretching from Texas to California (Mexican Cession) for a $15 million payment- Effect #1 * Californios and other northern Mexicans lost their livelihoods to the flood of American newcomers- Effect #2, Effect #3 * California enters the Union as a free state in Effect #4

* In 1853, America made the Gadsden Purchase to secure the border and make way for a new railroad