John Brown was an abolitionist. He is best known in American history as the man that led the failed attempt to steal munitions from Harper's Ferry in 1859. In Kansas he may be best known for the Pottawatomie Massacre.
Here is a link to an interactive time line hosted by PBS for their American Experience series. It shows from birth to burial John Brown's life.
After the raid, and Brown's execution, many northern abolitionists considered him a martyr to the abolition movement. The famous song "John Brown's Body" was used as a march during the Civil War by the Union troops.
John Brown's life is perfectly suited for the debate: Does the end justify the means?
Was John Brown justified for rebelling against his country, was he justified for avenging the raid on Lawrence, Kansas, or was John Brown just a loony murderer?