“Romantic love is a kind of spiritual breath each of us was raised on, hopes for, dreams of, and expects in our lives. Those of us who have it can scarcely imagine life without it, as if we’d suffocate for lack of oxygen.” —E.J. Graff

When asked why they got married, most people say that they fell in love. American society associates marriage with romantic love and lifelong companionship. For most of history, however, marriage was a contractual arrangement that had more to do with practicality than love. Marriage was the primary institution through which the rich exchanged property and the poor found their main work partner. However, in the nineteenth century, marriage changed dramatically from a practical arrangement to a satisfying personal relationship. The primary reason for this shift was that the Industrial Revolution enabled people to earn a living that...