Route 66 Sweetheart tells the story of a young woman growing up in Rutherford, New Jersey, in the 1930s. Marion (Mid) Lacy, who traces her ancestry back to the early New World Settlement of Nantucket, worries that she is overshadowed by more brilliant siblings and friends. In an era restricted by economic hard times and haunted by the prospect of approaching world war, she learns that all are counted in the creation of history, even the "sweetheart" of a distant admirer who travels "the Mother Road."