Singly and in small groups they straggled northward, travelling by night, hiding by day in thickets and swamps and, when fortunate, in a welcoming home that offered food and clothing. The fugitives were escaped southern slaves, their pursuers were slave-catchers and bounty hunters, their destination was freedom in distant Canada, and the zig-zag paths they followed from haven to haven were known collectively as the Underground Railroad.

A main trunkline of this amorphous "railroad" funneled slaves from the Carolinas, Tennessee, and Virginia through the District of Columbia and north across Montgomery County. Not surprisingly, numerous Sandy Spring Quakers, who had largely freed their slaves by the early 1800s and who often were ardent abolitionists, clandestinely opened their homes and outbuildings to the runaways.

Because of the secrecy surrounding the escape routes, much of the documentation of these sites is based on oral history. Often the remembered artifact is a trapdoor that led to a secret cellar, a tunnel that led from the home to an outbuilding, or a window candle that pointed north, toward freedom.