Tensions ran high over the question of slavery in the Western territories when Senator Charles Sumner rose to speak in 1856. The Massachusetts abolitionist let loose a fiery speech, denouncing expansion of slavery into Kansas. He attacked pro-slavery opponents by name—including Senator Andrew Butler of South Carolina.

Several days later, on May 22, Representative Preston Brooks, a relative of Butler’s, found Sumner sitting at his Senate desk. Raising his gold-headed walking stick, Brooks struck the Massachusetts senator repeatedly. Badly wounded, Sumner was unable to return to the Senate full-time for three years. His empty desk stood as a powerful symbol of the increasing North–South antagonism, an omen of the looming Civil War. Brooks resigned his House seat but was immediately reelected— then died shortly after.

"Sir, to assail a member of the Senate ... 'for words spoken in debate,' is a grave offense."
—Senator Henry Wilson of Massachusetts, May 23, 1856