Mexican-American War Took Place Between

Mexican-American War took place between 1846 and 1848 between the United States and Mexico just after the U.S.'s annexation of Texas, which Mexico still considered part of its sovereign territory. President Polk was a strong believer in territorial expansion, and American forces invaded New Mexico, the California Republic, and parts of what is now northern Mexico; the American Navy blockaded key ports and overran several areas on the Pacific Coast of Mexico; and another American Army captured Mexico City. This was expensive in terms of money and human resources, opposed by a number of Whig Party members, but eventually forced Mexico to cede the territories north of the Rio Grande to the United States in exchange for $18 million dollars and the forgiveness of debt owed to American citizens. This was certainly mitigated by the discovery of gold in California, resulting in the California Gold Rush and a fervent migration to California (Eisenhower, 2000).

The actual causes of the Mexican-American War are numerous -- some simply political and some territorial. One of the major reasons from a political and territorial standpoint was the issue of the Texas Revolution and the Republic of Texas. In the early 1800s, Moses, and then his son Stephen, Austin brought over 300 families to Texas. This began a steady migration into the area and at the time was an authorized colony of the Mexican government. Mexico thought that the anglo settlers would develop the land for agriculture and act as a buffer between Mexico and the still warlike Comanche Indian population. However, by 1829, so much immigration had taken place that the Americans outnumbered Mexicans in the Texas territory, prompting Mexico to increase tariffs on U.S. shipped goods, prohibit slavery, and reinstitute heavy property taxes. The settlers rejected Mexico's demands, and although officially Mexico closed the area to additional settlement, more and more Americans immigrated into the area (Feldman, 2004).

To properly understand why so many Americans felt it their right to immigrant, one must understand the social, political and cultural ideas of America in the early 1800s. The 1812 War with the British established that the United States was a viable political entity, and particularly after the Lewis and Clark expiditions, Americans were aware that a vast and open continent lay between the eastern seaboard and the Pacific Ocean. More an more immigrants were arriving from Europe, and the chance for a new life, open space and farm land continued to push people toward the West. The idea that Americans had the right to expand became known as Manifest Destiny that first appeared in print in 1845, but had been popular for decades prior. The idea was that American's "manifest desitiny [was] to overspread the continent allotted by Providence for the free development of our multiplying millions." In other words, God granted Americans the right to move West and take whatever land possible. This was echoed in President Polk's Innagural Address in 1844, in which he put forth the idea that America was destined to expand democratic institutions, and that this was a moral right. "It is confidently believed that our system may be safely extended to the utmost bounds of our territorial limits, and that as it shall be extended to bonds of our Union, so far from being weakened, will become stronger" (Manifest Destiny, 2005).