Winthrop D. Jordan, Miriam Greenblatt, and John S. Bowes, The Americans: A History (Evanston: McDougal, Little & Company, 1991), 337.
A number of dramatic incidents grealty inflamed Northern opinion about both slavery and the South. Early in 1851 a black man named Frederick Wilkins was working quietly as a waiter in a Boston coffeehouse. Suddenly he was seized by a Virginia slave catcher who knew him as Shadrach, a runaway slave. While Wilkins was being held for return to Virginia, a crowd of African Americans burst into the courthouse and led him away to safety. ... Several years later, federal troops lined the streets of Boston as a fugitive slave named Anthony Burns was marched from the courthouse to a ship waiting to carry him back to Virginia. A gigantic crowd of fifty thousand people hissed and shouted in protest.