Suspect 3: The Mexican Cession When the War with Mexico ended, the United States acquired1 a lot of new territory. Good for the United States, right? Not so fast. You see, many people were anxious to fulfill their country’s manifest destiny and move out west, but there was a problem! A big problem. People couldn’t decide whether or not to allow slavery in the new territories2. People from the North argued that slavery was immoral3, and that people should not be allowed to bring their slaves into the territories. People from the South, however, argued that the slaves were their property, and people can bring their property wherever they like. Still, other people believed that each state that was made from the territories should have been able to decide for themselves whether or not to make slavery illegal. Needless to say, the Mexican Cession (the land we took from Mexico) caused a lot of arguing. the Mexican Cession 1 acquired: gotten 2 territories: land owned by the United States that has not been made into a state yet 3 immoral: wrong