Black Brook is a tributary of the Merrimack River which flows to a gulf of what ocean?
Black Brook (Merrimack River): Black Brook is an 11.4 mi stream located in southern New Hampshire in the United States. Black Brook (Merrimack River):  It is a tributary of the Merrimack River, which flows to the Gulf of Maine. Gulf of Maine: The Gulf of Maine (French: "Golfe du Maine" ) is a large gulf of the Atlantic Ocean on the east coast of North America.
Atlantic Ocean