Thursday, December 6, 2012

GIS, General Lee, and the Future of Historical Cartography

Unless you’re a professional geographer, you’ve probably never heard of a tool called Geographic Information Systems, or GIS. Until recently, unless you were a student or faculty member at Middlebury College in Middlebury, Vermont, you may not have heard of Associate Professor of Geography Anne Kelly Knowles. Readers of the December issue of “Smithsonian” magazine know her as one of the recipients of the 2012 American Ingenuity Awards, given to individuals recognized for “brilliant new achievements in science, technology, art and society.”

According to the GIS website, the program allows geographers to take location-related data, integrate it onto a map, globe or chart, and analyze and display relationships and trends over a geographic space. I realize that this doesn’t sound very exciting. But the way that this program is being used takes it out of the functional realm of Cartography and into a variety of different fields, including History.

Using the GIS program, Professor Knowles has made new connections between geography and history, applying historical data to maps and topographical charts. For instance, an elevation map of Gettysburg, Pennsylvania, created in 1874. Using a scanned copy of the original, Professor Knowles created a highly detailed birds-eye view of the Civil War battlefield, highlighting strategic features such as buildings, roads, woods, and hills. By using robust GIS technology on an ordinary laptop computer, she was able to get the program to run a very complicated, but very revealing simulation.

Looking at the image, it’s hard to tell what all the fuss is about. You see elevations, some grayed out as if in shadow, some illuminated as if by the sun. You see landmarks infamous in Civil War lore; the Black Horse Tavern, the Union battle line, Little Round Top. The thing that stands out most, though, is a red dot marking the site of the Lutheran Seminary; the vantage point from which Confederate General Robert E. Lee stood to view the battlefield.

The illuminated parts of the landscape mark terrain that was within General Lee’s field of vision. The gray bits mark terrain that was hidden from Lee by Gettysburg’s hilly landscape. The GIS software has provided Professor Knowles (and 150 years of Civil War scholarship) with scientifically generated insight into Lee’s actions at the Battle of Gettysburg; actions that led to the Confederacy’s most iconic defeat.

For military historians, Robert E. Lee’s disastrous attacks on the second and third days of the battle have long been enigmatic. General Lee was one of the most celebrated generals on both sides of the conflict, a masterful commander with military experience dating back to the Mexican-American War. The terrain around Gettysburg should have suggested the danger of a frontal assault on Union lines. And yet, he made this mistake two days in a row.

To explain away Lee’s miscalculation, Civil War scholars have often criticized his subordinate general James Longstreet, the commander of the Confederate right. Longstreet has been accused of everything from incompetence to cowardice for his decision to lead his men on a protected but circuitous march on their way to attack the Union flank. But as Professor Knowles has shown, General Longstreet may have been able to see more of the battlefield and understand more about the tactical situation than General Lee did.

From his position near the Black Horse Tavern, Longstreet would have been able to see Union troops on top of the hill known as Little Round Top, the same hill that Lee had ordered him to attack. This pair of maps reveals that Lee had a very different understanding of the battlefield than did his subordinate, resulting in very different tactical decisions. Longstreet’s protected march may have saved the lives of hundreds of his own men, but it also delayed Lee’s strategic assault, allowing the Union line time to advance and prepare their defense.

Professor Knowles points out that the site where Longstreet’s men engaged the Federal defenders is illuminated, meaning that is was visible from the Lutheran Seminary. General Lee’s vantage point would have given him a good view of the bloody skirmish at the extreme end of the Confederate line, as well as Longstreet’s pained withdrawal. She speculates that the psychological pain of Lee watching his troops being killed may have affected his judgment the next day, when he ordered a costly frontal assault known as Pickett’s Charge.

GIS has also been used to examine Massachusetts history. The Director of the Salem Witch Trials Documentary Archive in Virginia, Benjamin Ray, has inserted data on the 1692 witchcraft accusations into an interactive map showing the spread and distribution of the disturbances. He notes that the progression of the accusations is similar to that of a disease. You can see the interactive map here.

And the possibilities of GIS go beyond historical cartography, as well. Scientists use the program to study the frequency and pattern of earthquakes. Similar studies are being conducted on the ozone layer and climate change. On an anthropological note, GIS has been used to determine that early hunter-gatherer tribes may have deliberately chosen to settle where they could see the landscape around them, a trait apparently not shared by agricultural societies.

The purpose of Geographic Information Systems is to take a range of data far greater than the scope of a single human being and to put it into a visible, spatial form. In essence, it visualizes human history, far more effectively and reliably than any painting or movie ever could. Perhaps even greater achievements lie ahead.

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You can see Professor Knowles' Middlebury College webpage here. Do you think that you have greater strategic and tactical talents than General Robert E. Lee? If so… are you General James Longstreet? If so… what’s your secret? How in God’s name are you still alive? Answers to all these and more can be left in the space below.


Ahmed, Akbar. “Cartography, Redefined.” Weekend. October 21, 2011.

Horwitz, Tony. “Mapping the Past.” Smithsonian. December 2012.

Symonds, Craig L. A Battlefield Atlas of the Civil War, 3rd ed. Mount Pleasant, SC: the Nautical and Aviation Publishing Company , Inc., 1994.

“What is GIS?” ESRI: Understanding our World. Web. 6 Dec. 2012.

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