In the years leading up to the Civil War, anti-slavery activists across the country worried that slavery was expanding. Numerous anti-slavery parties existed during the period, including the Free Soil Party and the American Party, but none was able to prioritize anti-slavery policies at the national level. By the 1850s, legislation like the Kansas-Nebraska Act so angered anti-slavery activists that they formed together into a single political party known as the Republican Party.

Westward Expansion

As early as the Louisiana Purchase in 1803, the status of slavery in the western territories ignited conflict between the North and the South. Northern free states did not want more slave states added to the Union because this would offset the North-South balance in Congress. Later, when the Mexican-American War erupted, Northerners feared that new territory acquired from Mexico would be home to slavery. Anti-slavery activists supported legislation like the Wilmot Proviso, which would have banned slavery in any new Mexican territory. Although this 1846 bill was blocked by a Southern-dominated Senate, it united anti-slavery activists and formed a foundation for the later Republican Party.

Compromises of the 1820s and 1850s

Starting with the Missouri Compromise in 1820, the North and South drew a line of latitude across the Louisiana Purchase at the 36ยบ 30' line. Only free states would be admitted from north of the line and slave states south of it, and for decades this compromise maintained peace between the sections. After the Mexican War, however, renewed interest in the expansion of slavery stirred controversy. This resulted in the Compromise of 1850, which banned the slave trade in the nation's capitol and strengthened the Fugitive Slave Law by requiring Northern states to return escaped slaves. These two compromises stalled the creation of the Republican Party for the time being, because anti-slavery forces were generally satisfied with their outcomes.

Kansas-Nebraska Act

The Kansas-Nebraska Act effectively shattered the peace brought by the Compromises of 1820 and 1850 by allowing settlers everywhere in the West to decide by a vote if slavery would exist in their states. This meant that new slave states could arise in both the northern and southern halves of the Western territories. For anti-slavery forces, this was unacceptable, and after its passage in 1854 they mobilized into a single party. Members of the Whig, Know-Nothing and Democratic parties who opposed slavery began to realize a need to collaborate as a single political party.

Origins in Ripon, Wisconsin

After the Kansas-Nebraska Act's passage in 1854, the first proto-Republican Party meeting took place in Ripon, Wisconsin. Members of the former Whig Party who opposed slavery gathered there, and christened themselves the Republican Party, a name that alluded to Thomas Jefferson's former Democratic-Republican Party. Two years later, the first Republican National Convention was held in Philadelphia, where John C. Fremont was nominated for the presidency. Four years after that, anti-slavery forces were firmly united in the Republican Party and Abraham Lincoln won the presidency.