Police say a group of young people were illegally drinking in the park. Four people are now charged.
It happened Sunday at Starved Rock State Park in Deer Park Township in LaSalle County.
Three 20-year-olds from southwest suburban Lockport are charged with unlawful consumption of alcohol. They are Gerard Ziomek, Vincent Piazza and Tracy Wagner.
Ziomek was injured in the fall but declined medical treatment.
A 21-year-old man was cited with unlawful entry.