Pierce signed into law the Kansas-Nebraska Act of 1854, which allowed settlers in those two territories to decide for themselves whether to outlaw slavery. Many in the North opposed this law because it led to the spread of slavery. Sponsored by Senator Stephen Douglas, the bill was designed to further progress on an intercontinental railroad, but devolved into a bitter dispute about the intractable slavery question. Opposition to the bill led to the creation of what became known as the Republican Party.

President Pierce believed that the states and territories had the right to decide for themselves whether or not to allow slavery. Because he was a Northerner who did not oppose slavery, he was sometimes pejoratively referred to as a “doughface.”