The Barnburners were a liberal faction of the New York state United States Democratic Party in the mid 19th century. The term barnburner was derived from the idea of someone who would burn down his own barn to get rid of a rat infestation.
The Barnburners opposed the extension of slavery, expanding public debt, and the power of the large corporations. They were led by Martin Van Buren, and in the 1848 presidential election they bolted the party, refusing to support presidential nominee Lewis Cass, and instead joining with other anti-slavery groups to form the Free Soil Party, which would nominate Van Buren for president.
Their opponents, the conservative Hunkers, favored minimizing the slavery issue, internal improvements, and state banks. The term hunker was derived from someone who "hunkers" (hankers) after a political office. Following the 1848 election, the Hunkers themselves split over the question of reconciliation with the Barnburners, with the "Softs," led by William L. Marcy, favoring reconciliation, and the "Hards," led by Daniel S. Dickinson, opposing it.
While this division relates primarily to New York politics, it also reflects on national divisions in the United States.