The water in the Pocomoke River is stained a tea-colored dark brown due to the tannic acid from fallen oak and cypress leaves. Ships heading back across the Atlantic in the 18th and 19th centuries collected water from the Nassawango Creek in barrels because the acidity tended to prevent spoilage on the long trip. This tannic acid content of the water played a role in another aspect of the Nassawango Creek; the production of bog iron. The acidic water leaches iron from subsurface sands and moves it through springs to the edges of the creek where it builds up a sandstone composite. An iron furnace was built in the late 18th century to smelt the iron and a company town arose in the middle of the cypress swamp.
The iron industry is gone now, except for the iron furnace itself, carefully preserved and surrounded by a recreation of part of the original town. Behind the furnace, where some of the iron ore was mined and a long canal runs to the creek., The Nature Conservancy’s Paul Leifer Nature Trail winds through the forest and over boardwalks through the swamp.