Contrary to what rangers and maps will lead you to believe...you can indeed hike down from a pull off area right past pretty place. Just follow my footsteps :p by no means am I encouraging novice trail hikers nor do I assume any liability if you choose to do so. When in doubt, just follow the water.
You can get to it via several trails, the closest one is starting on Jones Gap Trail from Jones Gap State Park. I'm not sure if there is a trail that connects to it from the YMCA camp but none of the trail maps or apps I have shows one.
As others have stated, there are multiple ways to reach the falls. The trail from Jones Gap is my most preferred, however, because it is great exercise, beautiful scenery and there is an absolute sense of accomplishment and reward once you reach Rainbow Falls.
You can access Rainbow Falls from other points in the parks, however it's a long distance. 16 or 17 miles. I know the YMCA brings kids in from the camp. I don't know how they do it.
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