Aerial photos for Iowa are available for every county beginning around 1940 and continue to the present. The resolution of the photos is high enough that individual buildings and even large trees can be discerned. These photos provide a birds-eye-view of exactly how the land has changed over the last 64 years.  One can see if woodlands have expanded or contracted and even if the density of the woodland has changed. What is cropland now may have been pasture 30 years ago, and buildings that existed in 1940 may now be gone.