There's a gate at the start of the road, but I don't believe they ever close it. Not terribly dangerous, but it may be a little sketchy crossing the creek and around the falls at night just due to low visibility
There are no gates that close, but you may run into wild animals, especially at night.
I have never seen the gate closed before and I have seen horse riding groups riding around the area at twilight. I would advise that you be careful of animals and snakes especially around dusk. A good headlamp will save your hiking plans every time you get caught in the woods with the sun setting. As already mentioned in other answers Creek crossings during dark can easily get dicey and you might get hurt by tripping on rocks so best to get that done before it gets extremely dark. Never climb up the Falls in low light. The ground can be highly unstable and rocks near the edges of Sill Branch Falls are mossy, algae covered, and quite slippery so anytime of day use discretion because getting help in Cherokee National Forest is iffy at best and make sure that someone knows where you are going in the woods.
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