The park, near Philadelphia, is closed amid the federal government shutdown.
The Park Service says runners and walkers have gotten only warnings, while those cited drove past barricades or blocked entrances.
Marathon runner John Bell of Chadds Ford says he did neither when he parked his car Sunday in a lot along state Route 23, which bisects the park and remains open. He plans to challenge his $100 ticket.
Bell says he knew the main parking lot was closed, but didn't know people couldn't run in the park.
Park Service spokesman Michael Litterst says safety is a concern given staff furloughs, especially after a hiker was injured last weekend at Acadia National Park in Maine.