We recently went live with the Forest Products Lab Atlas Collection. The Forest Atlas of the National Forests of the United States was originally published in 1913. The forest distribution information was compiled from a vast number of published records, partly from numerous unprinted reports, notes, and the knowledge of individuals whose observations were still unrecorded.
Most of these maps are hand colored but a few of the later maps were mechanically reproduced.
George B. Sudworth, along with his assistants in the Section of Forest Distribution, W. H. Lamb, Georgia E. Wharton, and Mary C. Gannett, compiled on separate cards many thousands of locality records for individual species, based upon published botanical lists, unpublished notes, and herbarium specimens. For each species these localities were plotted by number on a large cloth-backed contour map of North America.
Take a look at the maps and you will see the research that these foresters collected.