Answer:
In 1854, an uproar regarding the question of slavery in the territories challenged the relative calm after the Compromise of 1850. The pressure on this question came primarily from northern farmers, who wanted the federal government to survey the land west of Iowa and Missouri and put it up for sale. Promoters of a transcontinental railroad also pushed for this westward expansion.
Furthermore, many in the South were growing resentful of the Missouri Compromise, which established the 36° 30' parallel as the geographical boundary of slavery. Slaveholders entrenched themselves in defense of their “way of life,” which depended on the ownership of slaves, while also claiming that prohibiting slavery’s expansion ran counter to basic American property rights. They now contended that the question should be decided by popular sovereignty, or allowing the white residents of a territory to decide whether it should permit slavery when it applied for statehood. :)