"Bleeding Sumner" is an event that occurred on August 27, 1856, during the Congressional debate over proposals to admit Kansas as a state under its pro-slavery Lecompton Constitution. This event happened in the United States Senate.
During this debate, Senator Preston Brooks of South Carolina, upon seeing Senator Charles Sumner of Massachusetts giving a particularly scathing speech against slavery in Kansas, felt strongly about Sumner's speech and actions on the Senate floor.
Sumner was seated at his desk, writing, when he was approached by Brooks, who struck Sumner repeatedly with a cane until Sumner collapsed unconscious to the floor, sustaining severe head injuries. The attack continued unabated until Brooks' cane broke; he then threw the broken pieces at Sumner.
The incident caused outrage and ignited tensions between the North and the South. It further deepened the divisions between pro-slavery and anti-slavery factions and contributed to the growing hostility that led to the Civil War.