Trails change, become overgrown, washed out, etc. Things change, even topography. Even using a USGS topo map, look at the fine print and determine when the field work was performed.
I work routinely in an area mapped by aerial photography in 1938. With a couple of prominent exceptions, the topography is quite accurate. Cultural features like buildings, roads, and trails are a different matter. There is also the matter of human error and diligence. I have used recently issued maps based on recent aerial photography that were presumably field checked by diligent worker. It is pretty evident that at least some of the field checking occurred in a tavern somewhere..
one or more gifts or other benefits from the co-op.