The ideology of "Manifest Destiny" dates back to the first interactions between the Europeans and Native Americans. The belief convicted that colonizers were destined, by God, to conquer the territories of the Americas. Manifest Destiny justified using force and extreme measures to remove the native population from the colonizer's desired piece of land. James K. Polk was a firm believer in this ideology. Serving one presidential term, he worked to expand American territory. He essentially led the United States to victory over Mexico in the Mexican-American War. This led to the exchange of most of the modern-day southwest, from Mexico to the United States. 

     Although Polk's embrace of Manifest Destiny added land to the American territory, tensions arose between slaveholders and abolitionists and between white settlers and Native Americans. The North and South fought over whether the new southwestern states added to the country would be free or slave states. One would expect that after obtaining new territory as a result of the Treaty of Guadalupe-Hidalgo, Americans would have a boost of post-victory nationalistic pride and rejoice however a bitter feud grew. Abolitionists feared that cotton would be planted in this new territory which would lead to increased slavery. Slaveholders believed that if the states were proclaimed free and slavery was abolished, the south would lose power in Congress. Guadalupe-Hidalgo, the Gadsden Purchase, as well as many debates over whether other territories in the United States would be free or slave fueled the Civil War in order to settle the debate once and for all. 

     Native Indians that were originally settled in the Southwest territory frequently battled with the new Americans moving in. The Treaty of Guadalupe-Hidalgo states that Mexicans in the territory previously belonging to Mexico can stay where they are or they can move to Mexico but still retain their property. It also stated that those who remain can be Mexican citizens or US citizens but have to choose within a year; the default is US citizenship. With these terms, Mexicans were given the right to continue living where they were however, violent white mobs and landowners sought expansion, therefore using force and terrorizing the Mexicans to the point of expulsion from their homes. American settlers fought to manage the land and other important resources against long term residents. Many Mexicans, Mexican Americans, and Native Americans faced legal, cultural, and social prejudice and thus found it hard to defend their rights. Mexican American landowners were mostly forced to go to court by the U.S. government to prove they had claims to their territory. New settlers appeared to disregard the legal rules of Mexico also. White settlers also fought for land rights with American Indians.

     In conclusion, the interaction between the physical geography, human geography, and human-environment influenced the development of cultures, societies, and nations after the Treaty of Guadalupe-Hidalgo and other territorial expansions by pushing settlements around, increasing tension between slaveholders and abolitionists as well as creating opportunities for further violence between the Americans and the Mexicans. The culture of the land succeeded changed because of the new American settlers expelling Natives and Mexicans from the territory. From the obvious fact that with forced expulsion comes revolt, and the case that the Treaty of Guadalupe-Hidalgo was not being followed, battles between the settlers and previously settled arose. Along with this, the possibility of new cotton fields and the need for slaves would make the new territory slave states became a debated topic among slaveholders and abolishment. Evidently, from these events as well as other territorial disputes, America led itself into a Civil War which caused even more cultural, societal, and national change.