Boundaries: How the Mason-Dixon Line Settled a Family Feud & Divided a Nation by Sally M. Walker (review)

In early colonial times, before the New World settled into what came to be seen as an inexorable configuration of North/South, free/slave, red state/blue state, royal charters and land grants set borders that came up for dispute. Maryland’s northern border and Pennsylvania’s southern border were set at 40 degrees north latitude, but the surveying wasn’t yet exact enough to determine the line with precision. As descendants of the Calvert and Penn families squabbled over the border and settlers were doubled-billed for taxes, it became obvious that something needed to be done. Enter Charles Mason and Jeremiah Dixon, astronomer-mathematicians whose newfangled calculations based on celestial observation could set the records straight. Walker begins at the beginning, with substantive background on the founding of the bordering colonies, but the story really comes into focus with the challenges facing the first surveyors as they slog through swamps and over hills and across rivers to determine boundaries. Their failure brings the ingenious work of Mason and Dixon into relief, as the pair finds ways to address every obstacle that stymied their predecessors. Many history books for youth gloss over science and math in favor of a strictly human-interest approach, but Walker embraces the fields and walks readers through both the theory behind the calculations and the exhausting (and expensive) fieldwork it took to get results. Plenty of maps and diagrams support the text, and even math-resistant readers may find themselves learning more than they expected. The most appreciative audience, though, will be the kids who doodle in their notebooks through history class, just waiting for the bell to ring for math. Source notes, a bibliography, and an index are included.