The shutdown has closed the Philadelphia-area site, and local runner John Bell and others have gotten $100 tickets after parking there.
So they are holding a Patriot Run on Sunday.
Bell says they've been running on roads that cut through the park and remain open—just steps from the park's running path.
The National Park Service says at least 20 people have been issued tickets at Valley Forge, and more at parks across the country. A spokesman says safety is a concern, given staff furloughs.
But Bell doesn't believe safety is an issue at Valley Forge, which has wide paths and gently rolling hills.