Entry No. 48 — the Washington, D.C. file — filed under: ruins

Ruins of Clopper Mill

Located within Seneca Creek State Park, these three-story stone and brick ruins are all that remain of a water-powered gristmill dating back to the late 18th century. Expanded in 1834 by local businessman Francis Cassatt Clopper, the mill was destroyed by a devastating fire in 1947. Notably, Lincoln assassination co-conspirator George Atzerodt hid here for a night while fleeing Washington, D.C. in 1865.

The move: Park safely at a designated trailhead within Seneca Creek State Park and take a scenic walk to view and photograph the towering, ivy-draped stone walls from a safe distance across the creek.

📍 Before you go While the ruins are on state park land, there are no official trails leading directly to them, and the remaining three-story masonry walls are structurally unstable and unsafe to enter.

• 📍 Germantown
• 💸 Free
• ⚡ Low-key
• 🌗 Outdoors

Where: Intersection of Waring Station Road and, Clopper Rd, Germantown, MD 20874, USA

Hours: Added 2026-07-20 — confirm current access before you go.

Plan a visit & invite your people →

Further reading: Atlas Obscura · patch.com

last checked: 2026-07-20