Episode Details

In August 1846, during the Mexican-American War, President James K. Polk asked Congress for $2 million to negotiate with Mexico. Northern Democrats known as Barnburners, angry over lower tariffs, a vetoed internal improvements bill, and the Oregon compromise, had David Wilmot of Pennsylvania add a rider banning slavery in any territory taken from Mexico. The House passed it on a sectional vote that ignored party lines, breaking the unwritten rule against national debate over slavery.

In the Senate, Massachusetts Whig John Davis talked to run out the session, but the House clock was eight minutes ahead and the House adjourned first, killing both the money and the proviso. In 1847 Preston King reintroduced a broader version, and after the Senate stripped it out, 22 Northern Democrats switched under patronage pressure. The fight produced popular sovereignty, the Free Soil Party, and William L. Yancey's Alabama Platform. The episode ends with the irony that the 1860 census counted 29 enslaved people in Utah and none in New Mexico.

• The Missouri Compromise of 1820 had drawn the 36-30 line between free and slave territory.
• Henry David Thoreau refused to pay his poll tax over the war and wrote Civil Disobedience.
• The proviso's key clause ran to just 14 words.
• Lewis Cass proposed popular sovereignty in 1848, letting territorial settlers decide on slavery.
• California's gold rush led it to write a constitution banning slavery and skip the territorial stage.