Caltopo
I saw a reference to Caltopo in another post. I was not familiar with this site. It's topos are basically the same as the Nat Geo Topo!, but amazingly clearer. The boundary where two maps must be merged is obvious in Topo!, but much better blended by Caltopo. Check this example from the Big Pine trailhead. Caltopo has some gates not on Topo and the beginning section of the trail is actually shown. It's missing on Topo!. Thanks for calling this one to my attention.