Prior to the 1830's when Mexico was in the midst of their newfound independence from Spain, tensions mounted between the frontiersmen and the government of Mexico. Three main factors that caused the tensions in the frontier lands were the lack of government support, the demise of the Catholic Church, and the growing desire of each region to become sovereign nations. These tensions created weak nationalistic pride among the people of Mexico and paved the way for the U.S. to carry out their idea of Manifest Destiny. This idea of extending the U.S. from the Atlantic to the Pacific coast was not applauded by the people of the Mexican frontier, but many in the frontier realized that being a part of a rich and growing nation was better than being part of a nation that financially neglected and unfairly represented their lands.
The government of Mexico was unresponsive to the needs of the Mexican frontier.
During the many different governments that held power in Mexico, none offered solutions to problems such as attacks by Native Americans on Mexicans and the lack of representation in Mexican government. The lackadaisical treatment of the frontiersmen's needs by rulers such as Iturbide led the Mexican people to rebel against the Mexican government and treat themselves as independent. Iturbide was the self-proclaimed ruler of Mexico and shortly after gaining the throne took on the role of dictator. In the Plan of Casa Mata, orders were given to end Iturbide's rule of the country and replace it with a government that catered to the needs of the people. But this new government, with its good intentions of serving the people in such a way as the U. S. had done, still fell short of pleasing the frontiersmen. Frontier lands far from Mexico City such as Texas and California were getting enough strength to claim independence from Mexico and defend themselves in the name of their sovereign region. One classic battle is the battle of the Alamo, where the frontiersmen of the Republic of Texas fought off the Mexican forces for days before succumbing to the strength of the Mexican army. This dissatisfaction with the poorly run Mexican government spread quickly throughout the Mexican nation and the repercussions would result in the loss of nearly half of Mexico's territory.
The church in the Mexican frontier began to decay soon after the independence of Mexico. The Spanish clergy fled the areas of the frontier for more comfortable habitats near major civilized areas. This led to a lack of clergy in the frontier to run the churches and gain converts. The lack of churches and governments on the frontier lands made it easy for the U.S. to gain influence on the region and eventually take over the economy of the frontier lands.
The U.S. had a keen desire to stretch its boundaries from coast to coast. Mexico had every intention to keep the areas of California, Arizona, and New Mexico under their control, but made foolish decisions that ultimately destroyed their hopes of keeping the land. The people who resided in the areas that were desired by both countries claimed to be independent of either country. Therefore no one on the frontier wanted to be a part of either the U.S. or Mexico, but the sentiment was leaning toward the U.S. in terms of friendly trade and protection from enemies. It was merely circumstance that the U.S. would eventually gain the northernmost region of Mexico. Their superior army and economy took control of the land and provided trade that the Mexican government could not.