A map image that you might come across in our topographic map collection is an "orthophoto". In some locations, usually swampy areas, the U.S. Geological Survey did not create a regular map. Instead, they used an aerial photo of the area and overlaid some contour lines and other features. This creates a map much different in appearance from the normal USGS maps. This is the latest quadrange the USGS produced in that area, so it is the only map image we have.