This two foot pixel resolution black and white aerial photography was flown on various dates in July and August 1939. They were scanned in 2001, and georeferenced in 2002. 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 paper prints, local distortions (from the media stretching and/or shrinking) may be present as well as pen marks and fading. Caution should be used in interpreting features in this photography with reference to current conditions. In particular, many roads and road intersections have been realigned in the more than 60 years since this photography was taken. This historic aerial photography was captured in digital form as the result of a cooperative project between the Illinois State Geological Survey and the Geographic Information Systems (GIS) and Mapping Division of the Lake County Department of Information Technology. It is part of a statewide program to preserve the oldest known extensive aerial photography for future generations. The original photography was performed by the U.S. Department of Agriculture as part of a nation-wide program for use in agricultural assessment. Since the original negatives became unstable and were destroyed by the National Archives in the 1980's, only paper prints remain. A set of paper prints representing the best available quality was assembled from the collections of several agencies.