Introduction
For this midterm project, I chose to georeference a historical map titled Pennsylvania Railroad: Great Trunk Line and U.S. Mail Route. My goal was to place this historical railroad map over a modern map of the United States and examine how transportation networks were represented in the past. I was interested in how railroads connected different cities and regions, and how digital mapping tools could help us understand the historical development of transportation.
Sources
The main source for this project was a historical map from the Yale University Library digital collection. The map shows the Pennsylvania Railroad and its connections across the United States. I accessed the digitized image through its IIIF link, which allowed me to use it directly in Allmaps Editor. Since the map was already digitized, I did not need to clean a traditional dataset. Instead, I needed to identify the boundaries of the historical map and select geographical locations that could be matched with a modern map.
Processes
I used Allmaps Editor to georeference the historical map. First, I imported the image through its IIIF resource and drew a mask around the map to exclude the surrounding borders. I then selected eight control points by matching locations on the historical map with their corresponding positions on a modern map. Allmaps used a polynomial transformation to align the historical image with geographical coordinates. This process allowed me to compare the historical railroad network with modern geography. I encountered many challenges. I actually tried three different maps, but Allmaps had trouble accessing their website. Therefore, I landed on the current choice. Another challenge was finding accurate control points because historical maps do not always represent distances and locations in the same way as modern maps.
Presentation
For the presentation, I used ArcGIS’s All Maps Viewer to display the georeferenced map over a modern basemap. I wanted viewers to see both the original historical document and its geographical relationship to the present. The overlay makes it possible to compare historical and modern locations without changing the original appearance of the map. I also focused on keeping the map boundaries clear so that unnecessary borders would not distract viewers. The interactive interface allows users to zoom in and examine different regions of the railroad network.
Significance
I think this project demonstrates how historical maps can become useful sources for digital research. By georeferencing the Pennsylvania Railroad map, we can examine how railroad companies represented transportation networks and connections between different parts of the country. It also raises questions about which cities and routes received greater attention and how railroad companies presented their services to the public. For Digital Humanities, this project shows how digital tools can help us study historical materials. For me personally, this project serves as a stepping stone to greater projects, such as our final project. I hope to apply my skills learned from past lab assignments and the midterm to my future projects.
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