What do you do when you're 23, freshly out of college, and feeling lost? Taking a long walk seems like a reasonable answer. My friend and I walked over 3,400 miles, volunteering in every state we passed through, hoping to understand what Americans were struggling with—and in the process, we found ourselves. Fourteen years later, I'm retracing our route to share what kept us going on those long days and the one realization that changed our lives forever.