[citation needed] The river rises in northeastern Maine from the confluence of Millinocket Stream and Munsungan Stream in Maine Township 8, Range 8, WELS, in northern Penobscot County.

It runs through Ashland, and passes north of Presque Isle and east of Caribou.

It joins the Saint John River in Aroostook, New Brunswick, 2 miles (3 km) after crossing the Canada–United States border.

[citation needed] The United States government maintains two river flow gages on the Aroostook.

[6] Annual maximum flows occur during the spring snow melt and minimums in the fall.