Aerial photos are a must to go along with most USGS Topo maps. When you are looking at a topo map check to see when it was last updated. Many areas were orginally surveyed by the CCC in the 1930's. They do areial update once in a while. I was just looking at one last updated in 1975. The area has change dramatically since. Mostly thru some logging and fire access roads. The photos help alot.