Underground Railroad, secret network that helped U.S. slaves to escape from the South to the northern states and to Canada before the Civil War. Neither underground nor railroad, it was named for its necessary secrecy and for the railroad terms used to refer to its operation. Most of the “conductors” were slaves themselves, Harriet Tubman being one of the best known. Abolitionists, notably Quakers such as Levi Coffin, ran “stations” providing food and shelter along the way. Some 40,000–100,000 slaves escaped in this way.