I was just reading a request for fly fishing information from an out of the country angler who was visiting the USA and looking for instruction , bodies of water, and a fishing buddy.
If he wants ff instruction, bodies of water, fishing buddies - send him here. He'll get much more ff info here than off any map. We can interact to answer the inevitable 2nd, 3rd, & 4th followup questions.

I wouldn't start with maps. I'll bet there's almost a million lakes, ponds, river sections, etc... that will show up on any of the map sites. Finding the bodies of water on a map is not even a good starting point.

OTOH, the web is full of excellent ff info. Start on this site in the Great Rivers section, and search in the archives. Fly Fisherman Magazine website has articles about regions like Rocky Mt. There's tons more.