The Underground Railroad as a literal locomotive system is the primary speculative element of this work of alternative history. It is repeatedly referred to as the handiwork of Black people alone. Through this motif, Whitehead celebrates the strength and ingenuity of Black Americans, and also demonstrates the repeating refrain that Black people are the only ones who can truly save themselves and each other. While white Railroad operatives undoubtedly play crucial and compassionate roles throughout the narrative, it is repeatedly maintained that Black people, and Black people alone, built the actual railroad. Whitehead therefore asserts that, despite the horrors and brutalities of enslavement, Black people in America possess an indomitable strength, spirit, and will toward freedom.

Through the Underground Railroad’s existence as an actual rail line, Whitehead also indicts the concept of progress. The locomotive is one of the most recognizable symbols of American progress and is often seen as a beautiful symbol of the Industrial Revolution. By placing a train deep underground and casting its passengers as only able to see darkness, Whitehead turns the myth of American progress on its head. He foregrounds the fact that all the “progress” that America essentially attributes to white people was only earned through the pain and death of Black people, who must labor in literal darkness to secure their own freedom—which they must pursue in utter secret.