Salem, Massachusetts 01970Salem Maritime National Historic Site website
Derby Wharf Light Station has aided navigation in Salem Harbor since it was first lit in 1871. The Derby Wharf Light, along with the Hospital Point Light in Beverly, Massachusetts, and Fort Pickering Light Station on Winter Island in Salem, was designed to “mark the main channel leading into this anchorage, with the view to its becoming a harbor of refuge which may be safely entered at any time,” in the words of the 1870 report of the lighthouse board to the U.S. Treasury. The lighthouse is located at the end of Derby Wharf. Derby Wharf Light is about twelve feet square and about 20 feet high to the top of the cupola.
Originally, the light was powered by an oil lamp shining through a Fresnel lens. Fresnel lenses are designed to focus and intensify light, and are rated by orders, from first-order lenses that are used in the largest seacoast lights, and are almost nine feet tall, to sixth-order lights, which are about 17 inches tall. For many years, Derby Wharf Light had one of only 17 sixth-order Fresnel lenses in the United States. Today, the light is solar-powered, and the light is a red flash every six seconds.
Content from Salem Maritime National Historic Site website