The Republican Party grew out of opposition to the Kansas–Nebraska Act, which was signed into law by President Franklin Pierce in 1854. The Act opened Kansas Territory and Nebraska Territory to slavery and future admission as slave states, thus implicitly repealing the prohibition on slavery in territory north of 36° 30' latitude that had been part of the Missouri Compromise. This change was viewed by anti-slavery Northerners as an aggressive, expansionist maneuver by the slave-owning South. Opponents of the Act were intensely motivated and began forming a new party. The Party began as a coalition of anti-slavery Conscience Whigs such as Zachariah Chandler and Free Soil Democrats such as Salmon P. Chase.
The first anti-Nebraska local meeting where "Republican" was suggested as a name for a new anti-slavery party was held in a Ripon, Wisconsin schoolhouse on March 20, 1854. The first statewide convention that formed a platform and nominated candidates under the Republican name was held near Jackson, Michigan, on July 6, 1854. At that convention, the party opposed the expansion of slavery into new territories and selected a statewide slate of candidates. The Midwest took the lead in forming state Republican Party tickets; apart from St. Louis and a few areas adjacent to free states, there were no efforts to organize the Party in the southern states.
New England Yankees, who dominated that region and much of upstate New York and the upper Midwest, were the strongest supporters of the new party. This was especially true for the pietistic Congregationalists and Presbyterians among them and, during the war, many Methodists and Scandinavian Lutherans. The Quakers were a small, tight-knit group that was heavily Republican. By contrast, the liturgical churches (Roman Catholic, Episcopal and German Lutheran) largely rejected the moralism of the Republican Party; most of their adherents voted Democratic.
The new Republican Party envisioned modernizing the United States, emphasizing expanded banking, more railroads and factories, and giving free western land to farmers ("free soil") as opposed to letting slave owners buy up the best properties. It vigorously argued that free market labor was superior to slavery and was the very foundation of civic virtue and true republicanism; this was the "Free Soil, Free Labor, Free Men" ideology. Without using the term "containment", the Republican Party in the mid-1850s proposed a system of containing slavery. Historian James Oakes explains the strategy: =====
The federal government would surround the south with free states, free territories, and free waters, building what they called a 'cordon of freedom' around slavery, hemming it in until the system's own internal weaknesses forced the slave states one by one to abandon slavery. In Pittsburgh, Pennsylvania on February 22, 1856. This gathering elected a governing National Executive Committee and passed resolutions calling for the repeal of laws enabling slaveholding in free territories and "resistance by Constitutional means of Slavery in any Territory," defense of anti-slavery individuals in Kansas who were coming under physical attack, and a call to "resist and overthrow the present National Administration" of Franklin Pierce, "as it is identified with the progress of the Slave power to national supremacy." first national nominating convention was held in June 1856 in Philadelphia. John C. Frémont ran as the first Republican nominee for President in 1856 behind the slogan "Free soil, free silver, free men, Frémont and victory!" Although Frémont's bid was unsuccessful, the party showed a strong base. It dominated in New England, New York and the northern Midwest and had a strong presence in the rest of the North. It had almost no support in the South, where it was roundly denounced in 1856–1860 as a divisive force that threatened civil war.=====
The Republican Party absorbed many of the previous traditions of its members, who had come from an array of political factions, including Working Men, Locofoco Democrats, Free Soil Democrats, Free Soil Whigs, anti-slavery Know Nothings, Conscience Whigs, and Temperance Reformers of both parties. Many Democrats who joined were rewarded with governorships, or seats in the U.S. Senate, or House of Representatives.
During the presidential campaign in 1860, at a time of escalating tension between the North and South, Abraham Lincoln addressed the harsh treatment of Republicans in the South in his famous Cooper Union speech: ====
[W]hen you speak of us Republicans, you do so only to denounce us as reptiles, or, at the best, as no better than outlaws. You will grant a hearing to pirates or murderers, but nothing like it to "Black Republicans." [...] But you will not abide the election of a Republican president! In that supposed event, you say, you will destroy the Union; and then, you say, the great crime of having destroyed it will be upon us! That is cool. A highwayman holds a pistol to my ear, and mutters through his teeth, "Stand and deliver, or I shall kill you, and then you will be a murderer!"