So, a while ago, some coordinates were found on a gravity falls themed site, hidden behind a bunch of ciphers, and claiming to be the location of Gravity Falls:

https://www.google.co.uk/maps/place/44°47'36.7"N 121°33'23.0"W/@44.7929619,-121.5558566,240m/data=!3m1!1e3!4m2!3m1!1s0x0:0x0

post discussing the coordinates

Now, a lot of people have seen that, but don't believe it's enough evidence. Something I, and a few other people noticed, is this map: http://vignette2.wikia.nocookie.net/gravty-falls-viet-nam/images/f/fd/S1e1_gravity_falls_oregon_map.jpg/revision/latest?cb=20151203153830&path-prefix=vi

If you draw a straight line passing through Corvalis and La Grande, and another from Mt. Hood to Bly, the lines intersect over gravity falls. All of these locations are located at aproximately the same place in real-world Oregon. So if we do the same on a real map, the lines intersect about here:

https://www.google.co.uk/maps/place/Bly, OR 97622, USA/@44.6912592,-121.6545311,70649m/data=!3m1!1e3!4m2!3m1!1s0x54c901bf3e026471:0x343a62e693942fb4

Right in the middle of the Warm Springs reservation. The same place the coordinates lead. Try entering the coordinates on that link, and you'll see that it just zooms in.

So that's two pieces of evidence, one of them definitely from the show itself, that lead to the same area. If no one has gone there yet, and it looks like no one has, please do so as soon as you can. This could be it.