About 10 years ago we stayed at the KOA on Lundy's Lane. It was well run, clean, employees were polite, campground bathrooms were clean and maintained, kids playground area and equipment was in good shape. The public bus that goes to the falls stops right at the entrance.
We had a great time, and our kids enjoyed the campground.
I have no idea if the campground is still as good today.
Edited to add: We had dinner at the Skylon restaurant, and enjoyed it greatly! Good to really good food, and you can not beat the views!
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2021 F150 2.7
2004 21' Forest River Surveyor