Fort Mifflin - Revolutionary War fort with extant 18th‑century defenses

Fort Mifflin, located on the Delaware River, played a key role in the Revolutionary War by delaying British resupply during the 1777 siege of Philadelphia and endured heavy bombardment. Significant portions of its 18th‑century earthworks and some original structures survive, and the site is designated a National Historic Landmark. Fort Mifflin is often cited as one of the few Revolutionary War fortifications in the United States that retain visible period defensive works.