The annexation of Texas did not happen immediately though because of northerners worrying about adding another slave state to the union. It was not until James K. Polk was elected to office that Texas was actually annexed. This angered Mexico as Texas had originally belonged to them and they saw it as an act of war. Polk did not stop there though as when his offer to purchase disputed lands between the Rio Grande and Nueces River did not go through, he sent troops to the area. On April 25, 1846, a group of U.S Soldiers were attacked by Mexican Cavalry and were killed. This provided the grounds the Polk needed to start a war. After the attack Polk went to congress asking them to declare war, saying that the “cup of forbearance has been exhausted, even before Mexico passed the boundary of the United States, invaded our territory, and shed American blood upon American soil.” This led to congress officially declaring war on Mexico on May 13. 1846, even though there was much opposition to the decision from northerners. Another cause of the Mexican American War is slavery, as many of the southern slave states …show more content…
One of the biggest effects that the Mexican-American War had was the massive amount of territory that the United States gained from it. After America had won the war they received a huge amount of land from Mexico that was known as the Mexican cession. This land was an estimated 525,000 square miles and covered most of would would come to be the southwestern United States. This land covered many states such as California, Nevada, New Mexico, and Arizona. The land that Mexico ceded to the United States covered about two thirds of their total land and was estimated to be worth about 15 million dollars. Also, the Mexican-American war led to more disputes on whether the new territories should be slave states or free states. Even before the war was over there were already arguments about how slavery would be handled in these new territories. This was seen in the Wilmot Proviso, which said that any land acquisitioned from the Republic of Mexico would never see slavery or involuntary servitude. The Wilmot Proviso was created by a Northern democrat and helps to show the views that the north had, while the South wanted these new territories to be slave states. A compromise was made between the two and popular sovereignty was introduced in the new territories. Popular Sovereignty is the principle that the people choose what they want and that the people in these new