Which of the following was a reason the United States went to war with Mexico?

1. To set the boundary of the Mexican border at rio grande river
2. To make northern abolitionists happy
3. To gain more territory from Mexico, including California
4. To help president Polk keep his campaign promises

All of the above statements are true. Therefore, all of the options 1, 2, 3, and 4 were reasons why the United States went to war with Mexico.