Adam B. Sullivan, 19, was with a female companion about 2 a.m. at the popular vista that overlooks the Susquehanna River near Marietta, police said.
Cpl. Miles Bixler of West Hempfield Township Police Department said Sullivan's death appears to be accidental.
He said the woman, who was not identified, called 911 shortly before 2 a.m. after Sullivan fell.
Police believe the couple climbed over a fence intended to keep people away from the edge of the steep cliff.
Bixler said the woman told police they went to Chickies Rock Park to watch trains run on the tracks near the river.
The park closes at sunset.
Lancaster County Coroner Dr. G. Gary Kirchner said the victim died of multiple traumatic injuries and had numerous broken bones. He was pronounced dead at the scene.
Kirchner said no autopsy is scheduled. Toxicology results are expected within two weeks.
The fence was built around the summit of Chickies Rock Park in 1990. Signs warn visitors not to go beyond the fence.
The first rescue crew was dispatched to the site of the accident at 2:02 a.m.
"If I were (visiting) there, I certainly wouldn't go after dark," Kirchner said.
Although Chickies Rock offers a spectacular view of the river, York County and the borough of Marietta, it can be a dangerous place.
Newspaper records show 12 people have died from falls there since 1981.
Before the stone and wood-rail fence was built, Kirchner said deaths seemed to occur annually at the site.
Four deaths at Chickies Rock have been reported since the fence was built, according to newspaper records. Prior to Saturday's accident, the most recent death was in March 2003.
Chickies Rock Park is Lancaster County's second-largest regional park.
Funeral services for Sullivan are being handled by Burg Funeral Home in Red Lion.