Final answer:
Mexico abolished slavery in 1829, but American settlers in Texas desired it to become a U.S. slave state. After the Mexican-American War, the expansion of slavery in the newly acquired territories became a major point of contention between the North and the South.
Step-by-step explanation:
Mexico's position towards the institution of enslavement before the U.S. Civil War was complex. In 1829, Mexico abolished slavery, causing discontent among American settlers in Texas who had brought enslaved people with them. Mexico tried to accommodate the settlers by considering the enslaved workers as indentured servants, but the American slaveholders in Texas wanted Texas to become a new U.S. slave state. This led to a distrust of the Mexican government and a desire for Texas to join the United States as a slave state.
After the Mexican-American War, the issue of slavery in the newly acquired territories became a major concern. Southerners, who wanted to expand the institution of slavery, believed that slavery should be allowed in places like California and New Mexico, while Northerners disagreed. The differences between the North and the South were not primarily based on humanitarian concerns about slavery, but rather on the economic and political implications of slavery. This eventually led to the secession of southern states and the U.S. Civil War.
In summary, Mexico initially abolished slavery in 1829, which created tensions with American settlers in Texas. The issue of slavery in the Mexican Cession after the Mexican-American War further intensified the divide between the North and the South in the United States.