WE LIVE IN A WORLD OF BOUNDARIES.

Boundary stories are plentiful in newspapers, on television, and on the Internet. A country at war with itself divides into two separate nations. Religious boundaries lead to persecution. Cultural boundaries reflect the rich texture of diversity but also the tensions that arise when people misunderstand or misinterpret societal differences. Scientific boundaries range from the ethics of cloning to the exploration of new galaxies. All these boundaries — how they change and how they don’t — shape our world and who we are, as individuals and as members of the world community.

The story of the Mason-Dixon Line encompasses many different boundaries, some hundreds of years old. It begins with a country and the religious persecution of its own people. It becomes a property dispute. An escalating clash across cultural boundaries is part of the tale. So is surpassing a scientific boundary to achieve a feat many people deemed impossible. The line’s story slices through history and helps us understand how human perceptions and the course of a country change over time. It’s the story of how a political boundary became a symbol of freedom that helped shape the history of the United States. The tale of the Mason-Dixon Line reminds us to question the boundaries that surround us. And because it does, it is a tale for all times.

In some ways, the tale of the Mason-Dixon Line is a story of twos: two feuding families, two colonies in America, two kings named Charles, and two adventuresome surveyors. It’s also the tale of how nighttime skies steered daytime courses. To fully know the Mason-Dixon Line’s boundaries, you must know its roots. They begin in faraway places, then twist and turn in surprising new directions. They wind through heartbreak and triumph. And sometimes, without warning, they unexpectedly veer into danger.