Mexican American War Texas annexation; Mexico breaks diplomatic relations. Zachary Taylor is sent to Texas to start a war. We declare but New England threatens to succeed. The Wilmont Proviso says that no land gained from Mexico can be used for slavery. It looked like it went against the Missouri compromise. Zack Taylor and Winfield Scott becomes heroes. We take New Mexico and California. Santa Anna tricks Polk into getting Mexico back. In the final we take Mexico city. Treaty of Gualdapine This treaty ends the war, we get Texas California and Mexico. We get parts of Nevada, Wyoming, Utah , New Mexico,California. Most major participants in this war fight in the civil war. Zack Taylor becomes president because he is a war hero, America gets five hundred thousand miles of territory. The Gasden purchase This finishes the contiguous US. The cost is ten million. The purpose is to aquire land for a southern route for the trans-continental rail road. The civil war is when the actual rail road is built and it does not take a southern route.