Question: Which tributary of the Saint John River did Chamberlain Lake drained into 

Context paragraphs:
Saint John Ponds: The Saint John Ponds are a chain of shallow lakes at the headwaters of the Baker Branch Saint John River in the North Maine Woods.  The flow sequence is from the Upper First Saint John Pond, through the Lower First Saint John Pond, Second Saint John Pond, Third Saint John Pond, and Fourth Saint John Pond to the Fifth Saint John Pond.  Flow from one pond to the next is sometimes called Baker Stream rather than the Baker Branch Saint John River.  Great Northern Paper Company dug a canal from Fifth Saint John Pond 2 mi eastward to the North Branch Penobscot River in 1939, and built a dam at the north end of Fifth Saint John Pond so pulpwood logs harvested in the upper Saint John River watershed could be floated down the Penobscot River to Millinocket, Maine.  The canal and dam have fallen into disrepair so most drainage from the ponds again flows down the Saint John River.  All upstream ponds with the exception of the first had dams to regulate discharge flow for log driving, but those dams have similarly fallen into disrepair.  Moose use the ponds as summer refuge from heat and biting insects.

Baker Branch Saint John River: The Baker Branch Saint John River is a 48.0 mi river.  This river is a tributary of the Saint John River (Bay of Fundy), flowing in the Maine North Woods, in Maine, in the Northeastern United States.

Allagash River: The Allagash River is a tributary of the Saint John River, approximately 65 mi long, in northern Maine in the United States.  It drains in a remote and scenic area of wilderness in the Maine North Woods north of Mount Katahdin.  The name "Allagash" comes from the Penobscot word "/walakéskʸihtəkʸ/", meaning "bark stream".

Aroostook River: The Aroostook River is a 112 mi tributary of the Saint John River in the U.S. state of Maine and the Canadian province of New Brunswick.  Its basin is the largest sub-drainage of the Saint John River.

Nashwaak River: The Nashwaak River, located in west-central New Brunswick, Canada, is a tributary of the Saint John River.  It is 113 kilometres long.  The river rises from Nashwaak Lake (southeast of the village of Juniper) and flows south and east through uninhabited land and rapids to the village of Stanley.  From Stanley, the Nashwaak flows southeast to Nashwaak Bridge and Taymouth, then south the through several rural communities such as Durham Bridge, the historic town of Nashwaak Village and Penniac before it reaches the town of Marysville.  It flows into the Saint John River opposite downtown Fredericton.

Allagash Lake: Allagash Lake is in the North Maine Woods on the boundary of Maine range 14 townships 7 and 8.  Allagash Stream flows into the northwest corner of the lake from Allagash Pond, Crescent Pond, and Mud Pond in township 9 range 15.  Allagash Stream overflows the northeast corner of the lake and flows 5 mi through Little Round Pond into Chamberlain Lake.  Chamberlain Lake originally overflowed through Eagle Lake and Churchill Lake to the Allagash River; but was diverted through Telos Cut to the Penobscot River in the 1850s.  Allagash Lake provides good habitat for togue and squaretail.

Birch River (Maine): The Birch River is a 5.1 mi river in Aroostook County, Maine, in the United States.  From the confluence of its North Branch and South Branch ( ) in the southwest corner of the town of Eagle Lake, the river runs southeast to St. Froid Lake in Winterville Plantation.  The lake is drained by the Fish River, a tributary of the Saint John River.

Port of Saint John: The Port of Saint John is a port complex that occupies 45 ha of land along 3900 m of waterfront of the Saint John Harbour at the mouth of the Saint John River in the city of Saint John, New Brunswick, Canada.  The Port of Saint John, with facilities on both sides of the river, is noted for its extreme tidal range and river currents.  Because of the semi-diurnal tides and the river influence, slack water occurs at approximately half tide and not at high or low water as at most other ports.

Chamberlain Lake: Chamberlain Lake is one of the largest and deepest lakes in the North Maine Woods.  The lake originally drained north through Eagle Lake and Churchill Lake into the Allagash River tributary to the Saint John River.  Nineteenth-century logging operations diverted the lake into the Penobscot River before designation of the Allagash Wilderness Waterway in 1966.

Southwest Branch Saint John River: The Southwest Branch Saint John River (French: "Rivière Saint-Jean Sud-Ouest" ) is a 62.0 mi river in Maine and Quebec.  The branch originates in "Little Saint John Lake" ( ) on the international boundary between Saint-Zacharie, Quebec and Seboomook Lake Township 5, Range 20, WELS.  The branch forms the Canada–United States border as it flows northeasterly to a confluence with the Little Southwest Branch Saint John River in Seboomook Lake Township 9, Range 18, WELS.  The Southwest Branch flows briefly into Quebec ( ) and then through Maine to its confluence with the Baker Branch Saint John River in Seboomook Lake Township 9, Range 17, WELS.  The Southwest Branch finally joins with the Northwest Branch to form the Saint John River.

Supporting paragraphs: Chamberlain Lake Allagash River
Answer: The Allagash River