Picturesque canyons and seasonal waterfalls, great hiking trails
One reviewer stated that the only waterfalls are in St. Louis & LaSalle Canyons, which is simply not true. While the waterfalls are seasonal, being best after spring rains, 14 of the 18 canyons are known to have waterfalls at times. After a heavy early April 2017 rainfall, I encountered 12 waterfalls on a hike into just 3 canyons - Kaskaskia, Ottawa & Illinois, on the extreme eastern end of the park. Normally, those canyons have just one waterfall apiece. On the busiest holiday weekends, that may be one of the best areas to hike, if one wishes to avoid the crowds.
Check out Matthiessen State Park, Starved Rock's sister park about 2 miles south, during your visit. It's a bit more pristine and its waterfalls may be even more amazing than those at Starved Rock.
Please, however, preserve the fragile sandstone bluffs by refraining from "leaving your mark" and stay on marked trails, for your own safety. Each year multiple rescues are necessary due to people who attempt to climb the soft sandstone walls. Enjoy this beautiful natural area, but do it safely and leave no trace. Pack out what you bring in.