“Historians can now go back and—armed with this new evidence—think again about what may have influenced Lee’s decisions,” says Knowles.

A New Take on the Dust Bowl

To describe GIS, Knowles uses the analogy of a child’s flip book that builds layer upon layer of information pertaining to a specific spot on the globe. “The actual location is just the beginning,” she explains. Census data, weather reports, agricultural activities, geological information, voting records, public health files, railroad fares, birth announcements, land sales—the list of data that can be layered onto a GIS map is limitless. And GIS compiles not only information about a particular space but also information over time—making it possible to visualize changes occurring over months, years, and even centuries if enough data are available. Patterns of cause and effect can emerge that often go unnoticed in traditional archival-based research.

The University of Saskatchewan’s Geoff Cunfer used GIS to challenge the long-accepted scenario that the Dust Bowl was caused on the Great Plains in the 1930s by overfarming driven by a rapacious agricultural system. By employing the tools of GIS, Cunfer could look back before the Great Depression and analyze a much larger geographical area than previously surveyed. He discovered that dust storms had been a feature of prairie life for many generations. Aggressive farming may well have contributed to the dust storms of the 1930s, but it was not “the sole and simple cause of the Dust Bowl.”

The University of Virginia’s Center for Digital History has created an interactive website that demonstrates the power of GIS for everyday users. “VisualEyes” (www.viseyes.org) includes maps, images, charts, and text that enable the exploration, for example, of Thomas Jefferson’s travels in Europe, or the study of patterns of slave ownership in Texas across time. Another University of Virginia researcher, Benjamin Ray, has used GIS technology to map the geographical pattern of accusations during the Salem witch trials of 1692 (etext.virginia.edu/salem/witchcraft). The epidemic-like spread of accusers led Ray to a deeper understanding of religious and social tensions in Salem and surrounding communities.

The Industrial Revolution Reexamined

Knowles’s most recent project traces the evolution of the U.S. iron industry from small colonial-era forges to Pittsburgh’s giant steel mills. By mapping and layering data about coal deposits, fuel sources, iron ore deposits, labor forces, developing technologies, and transportation links from 1800 to 1868, she has created a “hybrid combination of history and geography” suggesting that industrialization in the United States was not nearly as rapid nor as consistently successful as often thought. While GIS mapping techniques helped her paint a nuanced and complex picture of the Industrial Revolution, she says that GIS technology alone would not have been enough. “The GIS database is just raw information. You have to be a historian to know which questions to ask.”

According to Richard White, founder of Stanford University’s Spatial History Project (www.stanford.edu/group/spatialhistory/cgi-bin/site/viz.php?id=379), some historians remain skeptical about GIS, uncomfortable with what they see as a departure from traditional, analytic, and narrative-based history. “In some ways, we’re still in

the missionary phase,” he says. “This is not the end of normal, narrative history,” he tells his colleagues. “It’s an add-on.”

Powerful computer technology is now lifting history off the printed page and into three dimensions, providing vivid new ways to glimpse into the past. But as historians and geographers both will attest, the ability to see history in its place generates just as many questions as answers.