Or maybe enough for a full week! Or return often. The three big falls are great and several smaller ones are very picturesque, like Wolf Creek or Shadow Falls (just a few steps past upper falls it get's missed sometimes). The river gorge is the star of course and you can easily get down to the riverbank - where the kayaks/rafts launch. If you can do stairs (286!) be sure to climb down to the bridge across the gorge/river just below lower falls. There are historic places like the Mary Jemison ('white indian woman of the Genesee') village site and the civil war encampment on the oft ignored west side of the park. Free admission btw on the west side with many trails and views (you can REALLY see Inspiration Falls from this side); it's just outside the Portageville exit to Letchworth Park.
Campsites are too open (especially for tenters) and disappointing, but do try to get a rustic cabin so you can explore the whole park and gorge. You'll need lots of time there.
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