I couldn’t put a plug out there for the Pignut Hickory fall color without also recognizing the Shagbark Hickory (Carya ovata.) It’s a little ahead of the Pignut in terms of peak fall color.
The main thing I’d like to highlight about this tree besides its color is one of its wildlife benefits. As you can hopefully see in the included pictures this tree has shaggy bark that peels back from the tree, hence the name Shagbark. Bats have been known to take shelter in this tree by crawling up under the shaggy bark peelings during the day, away from predators and the bright sun while they sleep.
Pictures taken at STLCC.