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 westwardOregon 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
1850- Effect #4
* In 1853, America made the Gadsden
Purchase to secure the border and make
way for a new railroad