A drive along any Interstate in Illinois will take you past fields of neatly planted corn and soybeans, across rivers and railroads flanked by rectangular ponds, and past cities and towns with new tract housing developments and manicured golf courses. While this scene has a beauty of its own, have you ever wondered what the landscape looked like when the first European settlers arrived? We are very fortunate to have a statewide record of what Illinois landscape was like when the first settlers arrived. Illinois was part of a vast tract of land known as the Northwest Territory (the land between the Ohio and Mississippi rivers and extending north around the Great Lakes). The Treaty of Paris ended the Revolutionary War in 1783 and gave the new nation the original 13 colonies plus the Northwest Territory. At that time the United States was independent, but badly in need of money. What better way to raise money then by selling land? However, before land could be sold, it had to be surveyed.
In Illinois, the surveys began in 1804 and were largely completed by 1856. As the surveyors moved across the state, charged with the task of laying out this rectangular grid system, they were required to keep field notebooks. In these notebooks they had to record details about their survey, such as the quality of the landscape, mines, salt licks, watercourses, springs, mill seats, and other "remarkable and permanent things." Once a township was finished, the surveyors were to make a map of the area. These plat maps and field notebooks contain a wealth of information about what the landscape was like before the flood of settlers came into the state. It is these plat maps that the Illinois Natural History Survey used to create a statewide digital dataset of what may be described as early 1800s land cover in Illinois.
Each of the more than 1,700 townships in Illinois has at least one version of
the original surveyor's map. Additional redrafted versions are also available
for most townships. The redrafted versions were created in the 1850s at the
regional General Land Office (GLO) office in St. Louis, Missouri.
Cartographers used the original maps in consultation with the field notebooks
to create a more complete map of the township. We used these redrafted GLO
maps for our land cover map.
Each GLO map was scanned from microfilm onto a laptop computer. We used Adobe Photoshop software and a Canon MS400 microfilm scanner to capture the images, saving them as TIFF files. The images were georectified, or spatially referenced against U.S. Geological Survey Digital Raster Graphic (DRG) images (i.e., scanned USGS 7.5- minute topographic quadrangle maps) by matching the township and section corners on GLO images to the corresponding points on the DRG. This process allowed us to digitized or "trace" the line work on the plat map using Geographic Information System (GIS) software (ESRI Arc/Info).
The scanned, georectified images of each
township are now a permanent archive
of the GLO maps. This will allow users to view the original plat
maps. The separate digitized version of the maps is a statewide GIS coverage,
which can be used on its own or as a layer in GIS analysis (Figs. 1 & 2).
The data from records of land cover of Illinois from the early 1800s will
provide valuable information in reconstructing a picture of Illinois' natural
history and lead to informed decisions concerning habitat restoration.
This two-year effort was partially funded by Illinois Department of Natural Resources, Office of Realty and Environmental Planning. The poster "Land Cover of Illinois in the Early 1800s" is available through the INHS Distribution Office at a cost of $6.42 (price includes domestic shipping) for single posters. Prices per poster may be cheaper when ordered in bulk. You can order the 26" x 36" color poster by mail from the INHS Distribution Office, Illinois Natural History Survey, 607 E. Peabody Dr., Champaign, Illinois 61820, or by phone at (217) 333-6880 or e-mail at rjohnson@mail. inhs.uiuc.edu. We also hope to distribute a digital version of the data on CDs or via the Internet.
Diane Szafoni, Diane Greer, Liane Suloway, and Janet Jarvis, Center for Wildlife Ecology; Kate Hunter, Center for Biodiversity
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