Sparkplug lighthouses are cast iron structures built at offshore locations. The keeper's quarters is a round building, usually three stories in height. The round lantern room sits atop the keeper's quarters, and the whole structure rests on a solid foundation, usually a concrete or stone caisson. The Harbor of Refuge Light at Lewes, Delaware, shown at right, is a typical example. Completed in 1926, it is also the last one ever built.
Because of their shape, these lighthouses have come to be called "sparkplugs." Before the day of gasoline engines, they were sometimes called "coffee pots." In many places they were called "bug lights," because at a distance they appeared short and broad, rather like a beetle on the surface of the water.
Sparkplugs were prefabricated, brought to the site by barge, and put in place by floating cranes. They were a low-cost solution to the problem of providing offshore lighthouses in the sounds and bays of the northeastern and mid-Atlantic states, where all but three of the surviving examples are located.
Harbor of Refuge, Delaware;
photo courtesy of Bob Trapani,
Delaware
River and Bay Lighthouse
Foundation
