Answer:
With the end of the Mexican War in 1848 and the Treaty of Guadalupe Hidalgo, America was ceded western territories. This posed a problem. As these new territories would be admitted as states, would they be free states or those that practiced enslavement? To deal with this, Congress passed the Compromise of 1850, which basically made California free and allowed the people in Utah and New Mexico to choose for themselves. This ability of a state to decide whether it would allow enslavement was called popular sovereignty.
Step-by-step explanation:
While the American Civil War (1861–1865) was devastating for the United States in terms of human loss of life, it was also the event that caused the American states to finally become united.
Enslavement—the "cruel, dirty, costly and inexcusable anachronism, which nearly ruined the world's greatest experiment in democracy," as American historian W.E.B. DuBois wrote—is often given as a one-word answer for the cause of the Civil War. But although it was the key catalyst, as historian Edward L. Ayers has said, "History does not fit on a bumper sticker."
A variety of events prompted the war, not just the underlying issues of enslavement and states' rights. From the end of the Mexican War to the election of Abraham Lincoln, the war’s roots were numerous and diverse.