During the 1850s, tensions between the North and South increased as the nation decided to how to incorporate the vast territories that had been acquired during the Mexican-American War of 1846-1848. The question of whether each territory was to be slave or non-slave worsened sectional tensions. In the end, a tenuous compromise was worked out, and California was admitted to the union as a free state, while the New Mexico and Utah Territories were allowed, through the process of popular sovereignty, to decide whether the states should be free or slave states. The slave trade was banned in the District of Columbia, and a more vigorous Fugitive Slave Law was enacted. This law in particular angered the abolitionist northerners who had witnessed escaped slaves being taken back to the south in chains. 

Later, in 1854, the Kansas-Nebraska Act caused an inflammation of sectional tensions, as these territories were also permitted through the process of popular sovereignty to decide whether to allow slavery or not. This act revoked the earlier Missouri Compromise of 1830, which had disallowed slavery north of the 36-30 line. Kansas became engulfed in a bitter and bloody war between defenders and opponents of slavery. Both abolitionists and defenders of slavery felt that their hold on power was under attack, pushing the country closer to the Civil War. 

There were many events in the 1850s that increased tensions between the two regions of the United States.  Basically, those events all served to set North and South against one another.  They caused the two regions to believe that they had different values and different interests.

Some of the events of the 1850s caused the two regions to feel that they had different values.  These events reduced their feeling of being essentially similar to one another.  Some examples of this were the Fugitive Slave Act, Preston Brooks’s attack on Charles Sumner, and the Dred Scott decision (the part of it which said that African Americans could never be citizens).  None of these events tangibly hurt the North or the South.  However, they played up differences in attitudes between the two.

Some of the events of the 1850s caused the two regions to feel that they had different tangible interests.  The fight over the Compromise of 1850 (over which areas of the Mexican Cession would be free or slave) was like this.  So was the fighting in “Bleeding Kansas.”  In both cases, these were fights over political power in the country as a whole. 

Both of these kinds of conflict led to increased feelings of tension between the two regions of the country as they came to feel that they had different values and different tangible interests.