|Location||Maine, United States|
|Coordinates||44°3'36", N 69°0'0" W|
|River sources||Penobscot River|
|Ocean/sea sources||Atlantic Ocean|
|Max. depth||145 meters|
Penobscot Bay originates from the mouth of Maine's Penobscot River. 11,000 years ago, at the beginning of the Holocene era, the Gulf of Maine's sea level fell as low as 180 feet (55 m) below its present height. Penobscot Bay was then a continuation of Penobscot River that meandered through a broad lowland extending past present day Matinicus Island.
Penobscot Bay and its chief tributary, Penobscot River are named for the Penobscot Indian Nation, which has continuously inhabited the area for more than ten thousand years, fishing, hunting and shellfish gathering in and around the bay and river. A part of the Wabanaki Confederacy, the Penobscot Indian Nation's present reservation includes Indian Island, north of Orono, Maine, and all the islands of Penobscot River above it. Ancient remains of their campsites dating back millenia have been found on the bay's shores and islands. For more on Wabanaki culture and history on the Maine coast, see "Asticou's Island Domain: Wabanaki Peoples at Mount Desert Island 1500-2000,"(National Park Service, 2007)
There are many islands in this bay, and on them, some of the country's most well-known summer colonies. The bay served as portal for the one time "lumber capital of the world," namely; the city of Bangor.
Islands in Penobscot Bay 
- Isle au Haut
- North Haven
- Matinicus Isle
- Sears Island
- Great Spruce Head
- Nautilus Island
- Little Deer Isle
- Deer Isle (Stonington, Mountainville, Sunrise, Sunset)
Towns along the western side 
- Saint George
- South Thomaston
- Owls Head
- Searsport (Penobscot Marine Museum)
- Stockton Springs
- Verona Island
Towns on the eastern side 
Penobscot Bay panorama 
- Barnhardt, Walter. A., Gehrels, W. Roland, Belknap, Daniel F., and Kelley, Joseph T., 1995, Late Quaternary relative sea-level change in the western Gulf of Maine: Evidence for a migrating glacial forebulge: Geology, v. 23, no. 4, p. 317-320.
- Maine Department of Conservation. "Penobscot Bay 10,000 Years Ago. http://www.maine.gov/doc/nrimc/mgs/explore/marine/sites/may99.htm
- Maine Department of Conservation. *"Penobscot Bay 10,000 Years Ago."
- Godfrey, John E. *The Ancient Penobscot, or Panawanskek. as transcribed from The HISTORICAL MAGAZINE and Notes and Queries concerning The Antiquities, History, and Biography of America. (Third Series, Vol. I, No. II; Whole Number, Vol. XXI, No. II) February, 1872. (Morrisina, N.Y., Henry B. Dawson) pp. 85–92 (illustrated & annotated)
- "Joshua Treat, The Pioneer Settler on Penobscot River." The Bangor Historical Magazine, vol. 4, 1888-1889.
- "The Farnsworth Museum"
- "The Penobscot Marine Museum"
- "Penobscot Bay Watch [NGO web portal on Penobscot Bay management, conservation, ecology, history and advocacy."