Dan McLaughlin of National Review Online marked the Republican Party’s March 20 birthday with a column correcting the record about the party’s origins.

This day in 1854, what became the Republican Party was founded in Ripon, Wisconsin. The process that led from the collapse of the Whig Party between 1850-54 and the rise of the Republicans as their replacement between 1854-60 was a complicated one, and there were times when it appeared that the anti-immigrant American Party (aka the “Know-Nothings”) might become the chief rival to the Democrats instead. The 1854 midterms led to the election of a House majority opposed to the Democrats and their agenda, but nowhere close to a single, unified party caucus. Indeed, as is often true of the beginnings of large things, the meeting in Ripon is only clear in retrospect as the birth of a new, national political party.

The chief driving force uniting the early Republicans was opposition to the Kansas-Nebraska Act, introduced in January 1854 by Democratic senator Stephen Douglas and supported by Democratic president Franklin Pierce, who signed it into law in May of that year. Kansas-Nebraska was universally understood to be a plan to open territories north of the Missouri Compromise line to slavery. Coming as it did on the heels of the Fugitive Slave Act controversies of 1850-51, which showed federal power at work for slavery in the North, the prospect of slavery’s territorial expansion, and of the breaking of the fragile peace on the issue of the Compromise of 1850, proved a radicalizing event for a lot of northerners who had always disliked slavery but were not previously motivated to do much about it.

To this day, there are those who seek to deny the extent to which opposition to the expansion of slavery was central to early Republican ideology – what historian Eric Foner summarized as a party of “Free Soil, Free Labor, and Free Men.”