On a direct line, Penobscot Bay lies about 150 miles northeast of Boston, midway along the coast of Maine. At its entrance it stretches about 30 miles across and is about the same distance from the sea to its head, where the Penobscot River empties. The river is wide and deep enough to be navigable for almost 60 miles, all the way to the present city of Bangor. Along the northeast shore of the Bay, 10 miles from the river, there is a small (1 ½ miles long by 3/4 mile wide) rocky finger of land that juts out into the water. It was then called Bagaduce (today it is known as Castine) and was the key to control of the entire Bay.
"Disaster in Penobscot Bay,"
Naval War College Review: Vol. 32:
1, Article 8.
Available at: https://digital-commons.usnwc.edu/nwc-review/vol32/iss1/8