President Abraham Lincoln said he was a "misguided fanatic" and Brown has been called "the most controversial of all 19th-century Americans."His attempt in 1859 to start a liberation movement among enslaved blacks in Harpers Ferry, Virginia, electrified the nation, even though not a single slave answered his call. He was tried for treason against the state of Virginia and hanged, but his behavior at the trial seemed heroic to millions of Americans. Southerners alleged that his rebellion was the tip of an abolitionist iceberg and represented the wishes of the Republican Party, but those charges were vehemently denied by the Republicans. Historians agree that the Harpers Ferry raid in 1859 escalated tensions that a year later led to secession and the American Civil War.
Brown first gained attention when he led small groups of volunteers during the Bleeding Kansas crisis. Unlike other Northerners, who advocated peaceful resistance to the pro-slavery faction, Brown demanded violent action. His belief in confrontation led him to kill five pro-slavery southerners in what became known as the Pottawatomie Massacre in May 1856, though it should be noted that this was certainly not the first use of violence in Kansas. Brown's most famous deed was the 1859 raid he led on the federal armory at Harpers Ferry, Virginia (in modern-day West Virginia. During the raid, he seized the federal arsenal, killing seven people (including a free black), and injuring ten or so more. He intended to arm slaves with weapons from the arsenal, but the attack failed. Within 36 hours, all of Brown's men were killed or captured by local farmers, militiamen, and U.S. Marines led by Robert E. Lee. Brown's subsequent capture by federal forces, his trial for treason to the state of Virginia, and his execution by hanging were an important part of the origins of the American Civil War, which followed sixteen months later. His role and actions prior to the Civil War, as an abolitionist, and the tactics he chose still make him a controversial figure today. Depending on one's point of view, he is sometimes heralded as a heroic martyr and a visionary or vilified as a madman and a terrorist.
Brown's nicknames were Osawatomie Brown, Old Man Brown, Captain Brown and Old Brown of Kansas. His aliases were Nelson Hawkins, Shubel Morgan, and Isaac Smith. Later the song John Brown's Body became a Union marching song during the Civil War.