The Underground Railroad was a network of secret routes and safe houses used by African-American slaves in the United States to escape to free states and Canada with the aid of abolitionists and allies who were sympathetic to their cause. The term 'Underground Railroad' is also used to refer to the abolitionists, both black and white, free and enslaved, who aided the fugitives. The term 'SUBWAY' is often used as a synonym for the Underground Railroad, as it was a means of transportation used by many of the slaves to escape.