Chatham Lighthouse, known as "Twin Lights" prior to 1923, is a lighthouse in Chatham, Massachusetts, near the "elbow" of Cape Cod.
The station was established in 1808, the second light on Cape Cod. To distinguish it from Highland Light, the first Cape Cod light, and to act as a range, twin octagonal 40 ft (12m) wooden towers were built. They were on skids so that they could be moved to keep them in line with the entrance channel as it shifted.
1841: The wood octagons were replaced with 40 ft (12m) brick towers
1857: Fourth order Fresnel lens installed.
1879: Current structures, of brick lined cast iron, were built.
1923: Northern tower of the pair was moved roughly 12 miles north to become Nauset Light.
1939: Chatham Light, which had been kerosene fueled since 1882, became electric.
1969: Fresnel lens was replaced with a Carlisle & Finch DCB-224 rotating light generating over 2.8 million candlepower.
1982: Automated, now one of the few lights that operates 24 hours a day.
The former keeper's house is an active U.S. Coast Guard station, and on-duty personnel living quarters. Search and Rescue, maritime law enforcement, and Homeland Security missions are carried out here. Flotilla 11-01 of the U.S. Coast Guard Auxiliary operates from this station.