Before street art became mainstream, the anonymous outlaws of "freight writing" put graffiti on the map. One of the most extreme and risky iterations of the art form, freight train graffiti culture has a rich history, laden with myth-like artists, remarkable romances and competitive graffiti crews. Delving into the underground subculture reveals the deep connection between graffiti and the American landscape, as well as the artists' obsession with putting life and limb on the line to make their voices heard.—SHOWTIME