Pennyslvania's Boundary: David Rittenhouse, Hero, Lord Baltimore, Villain

In the Twenty-first Century, now that we know how every American creek and river runs, we can see that it should have been pretty simple to establish a reasonable boundary between the royal grant to William Penn, and the grant to Lord Baltimore. Essentially, Penn had been given the Delaware Bay and a lot of wilderness to the West of it. George Calvert, Lord Baltimore, had been given the top half of Chesapeake Bay and a strip of wilderness to the West of it.

Odessa, Delaware

At what is now Odessa, Delaware, the two bays are only about five miles apart. A reasonable spirit of compromise should have settled the issue quickly. However, back in England, they were changing kings and beheading them over matters of religion. Lord Baltimore probably thought an opportunity to improve on his land grant might emerge from the turmoil if he just stalled long enough for matters to go his way. As we have noted elsewhere, the last word from the last king was what mattered. All this talk about justice, fairness, and astronomy was just idleness. So the Calvert family lawyers, over the course of eighty years introduced one specious proposition after another that turned other lawyers purple with rage.

Euclidean Geometry

It must be admitted that a lot of honest confusion was possible. Sometimes, a line of latitude was a line in the sense that Euclid intended: all length and no width. Sometimes, lawyers and kings were talking about "parallels" as if they were strips, roughly sixty miles wide. If that was really the intention, it was important to specify whether a grant extended to the southern edge of the strip, or to the northern edge. But in fact, the state of science in the Seventeenth Century was such that there was uncertainty both about where the strips were, and how wide they were. And if your language didn't make it clear whether you were talking about strips, or width-less lines, eighty years is a comparatively short time for a court to decide the case. To be fair to Lord Baltimore, a lot of people at the time didn't think these matters were capable of solution, so the traditional way of dealing with disputes was either by force or by bribery.

However, in William Penn the folks from Maryland were dealing with a friend of the King, who had one of the most brilliant mathematicians in Western civilization as his adviser. David Rittenhouse may have been born in that little farmhouse you can still visit on the Wissahickon Creek, and made his living as a clockmaker, but his native talents in mathematics, astronomy surveying, and instrument construction were so deep and so varied that later biographers are reduced to describing him merely as a "scientist" and letting it go at that. If you want to sample his talents, spend an hour or two learning what a vernier is, and then see if you could apply that insight, as he did, to a compass. So, as it turned out, Rittenhouse was able to describe a twelve-mile circle around New Castle, Delaware, construct a tangent that divides the Delmarva's Peninsula in half, and match it up with a Westward line we now call the Mason Dixon Line. When they finally got around to laying these lines on the ground, Mason and Dixon cut a twenty-four foot swath through the forest, using astronomical adjustments every night, and laying carved marker stone every fifth of a mile for hundreds of miles. The variation from the line devised by Rittenhouse was at most a fifth of a mile off the mark. The survey by Mason and Dixon was not quite completed by them because the Indians, curious at first, eventually became wild with suspicion at such behavior, particularly the part about going out and aiming cannons at the sky every night. It seems likely that George Calvert, Lord Baltimore, had no more confidence in this madness than the Indians did.

So, the next time you take the train from Philadelphia to Washington DC, you should reflect that strict reading of the words in the land grants did admit the possibility that your whole trip could either have been within the State of Maryland, or else in the Commonwealth of Pennsylvania, depending on whether lawyers or scientists had triumphed in this dispute. Since the Mason Dixon Line eventually divided not merely two states, but two violently opposed cultures, Rittenhouse must stand out in history of one of those people who was so smart that most people couldn't understand how smart he was.

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