When Billy introduces the Lincoln Highway as the route via which he and Emmett might retrace their mother’s footsteps and locate her in San Francisco, the highway is initially presented in its essential form as a concrete transcontinental roadway, but the highway becomes a symbol with greater layers and deeper significance as the novel progresses. After finding their mother’s postcards, Billy was able to deduce from their postmarks that she had traveled the highway as she mailed them to her sons after her departure from their home and their lives. To Billy, the highway symbolizes the possibility that he and Emmett may find her if only they retrace her steps by following the clues he believes she left for them. It is through Billy that Emmett hears of the highway for the first time. Emmett had planned to begin his new venture as a carpenter in Texas, where he thought the housing market promising enough to support the growth and success of his business venture.

The notion of San Francisco and the concept of the Lincoln Highway as introduced by Billy represents a novel future that Emmett had not considered, a complete change in their lives’ geographic trajectory as he had imagined it while in Salina.