| A | B |
|---|
| The evasion of the slavery issue by Whigs and Democrats in 1848 | Led to the formation of new antislavery party, the Free-Soilers |
| The California gold rush | Made the issue of slavery in the Mexican Cession areas more urgent |
| The Underground Railroad | Aroused southern demands for an effective fugitive-slave law |
| The Free Soil Party | Prepared the way for the antislavery Republican Party |
| The Compromise of 1850 | Created a short-lived national mood of optimism and reconciliation |
| The Fugitive Slave Law | Aroused active Northern resistance to legal enforcement and prompted attempts at nullification in Massachusetts |
| The Pierce administration's schemes to acquire Cuba | Fell apart after the leaking of the Ostend Manifesto |
| The Gadsden Purchase | Heighten competition between southern and Northern railroad promoters over the choice of a transcontinental route |
| Stephen Douglas's indifference to slavery and desire for a northern railroad route | Led to the passage of the Kansas-Nebraska Act, without regard for the consequences |
| The Kansas-Nebraska Act | Caused a tremendous northern protest and the birth of the Republican party |
