This is a great essay on the causes of the Mexican War.

Causes of the Mexican War The Mexican War lasted from 1846-1848 in the area now known as Texas. What began as several small disputes eventually led into an armed conflict between the considerably new nations of Mexico and the United States. The geographical and political disputes are the most likely causes of the war. These causes of this war became significant, when the outcome gave the United States a platform to become one of the …

…in the hands of a superior people for its "beneficent utilization". Some were outraged by the Mexican attack on American troops on "American soil" on May 9,1846" Rappaport pg 11. Issues like New Mexico, California, slavery, and other less important reasons were all apart of causing the Mexican War. The results of the Mexican War led America to gaining a few territories, but the long term affect that it had on America can still be seen today.