This two foot pixel resolution black and white aerial photography was flown on various dates in July 1946 by the United States Geological Survey. They were then scanned by the USGS and georeferenced by Lake County in 2007. This data should NOT be used at a scale larger than 1 inch = 400 feet. Due to the lack of sufficient camera calibration information, errors will increase towards the margin of each underlying photo, although this effect has been minimized by cropping individual photos to make this mosaic. Since these photos were scanned from old film, local distortions (from the media stretching and/or shrinking) may be present as well as fading. Parts of the county were not captured including some areas in Buffalo Grove, Highland Park, and Riverwoods. The date of the flight means that most trees have fully leaf-out canopies, which obscure some ground features. This flight took place during a period of high population growth and land use change. The census population of Lake County was 121,094 in 1940 and 179,097 in 1950, a 48% increase; this photography documents land use in the middle of that decade.