Mill Creek, in the old inner suburbs of Philadelphia, once powered as many as 23 mills. The ruins of several of those are still standing, along with an intact small 19th century mill on what was the oldest continuously occupied industrial site in the U.S., until it was finally abandoned in the 1990s. However this is a 'nature' picture; no ruins, and only a hint of the large amounts of rock and debris that wash downstream in the floods that are increasingly frequent now that much of the Mill Creek watershed has been paved.
