John Mason escaped from slavery in Kentucky and later became an Underground Railroad conductor. He escaped in the 1830s when he was about 12-years old and settled in Ohio. He worked as a waiter to pay his way through Oberlin College, graduating in the 1840s.
Soon after he graduated, he became an Underground Railroad conductor. It has been estimated that he helped more than 1,000 slaves to freedom in Canada.
Mason was later captured and returned to his former slaver in Kentucky, who sold him to a buyer in New Orleans. Mason later escaped, taking another slave with him, and made his way to Canada.
For more see The Underground Railroad from Slavery to Freedom, by W. H. Siebert, et al. [available full-text at Google Books]; and chapter 5, "Egypt's Border," in Front Line of Freedom, by K. P. Griffler.