The Deer Island Thorofare Lighthouse stands 52 feet above East Penobscot Bay and The east entrance to the Deer Island Thorofare. The lighthouse casts a flashing white signal into the surrounding waters every six seconds and a horn signal can be heard every 15 seconds during periods of foggy weather.

The lighthouse is constructed of brick with a white and black finish on the outside. There are no other buildings standing today on the property.

The Deer Island Thorofare Lighthouse was constructed on Mark Island at the east end of the Deer Island Thorofare in 1857, The United States Coast Guard automated the lighthouse in 1958, and replaced the old fourth order Fresnel lens with a new 250mm acrylic optic.

Use NOAA Chart13005.

Poised on Mark Island, The Deer Island Thorofare Lighthouse marks the east entrance to the Deer Island Thorofare off of East Penobscot Bay. On approach from East Penobscot bay, keep an eye out for The Born Cow and West Mark Island Ledge, the latter of which is marked by a nun buoy.

Local Notices to Mariners are now available exclusively online from the U.S. Coast Guard.

Unfortunately, the lighthouse is not open to the public, but it can be nicely viewed from the water by boat.