Question: What County that was incorporated on June 25, 1789 and named for John Hancock, has a short stream  from its source the river runs 5.4 mi south to its confluence with Mill Brook in Eastbrook?

Context paragraphs:
Little Seboeis River: The Little Seboeis River is a short stream in Maine Township 4, Range 7, WELS, Penobscot County, Maine.  From its source ( ), the river runs 5.5 mi south and west to its confluence with the Seboeis River.

Hancock County, Maine: Hancock County is a county located in the U.S. state of Maine.  As of the 2010 census, the population was 54,418.  Its county seat is Ellsworth.  The county was incorporated on June 25, 1789 and named for John Hancock, the first governor of the Commonwealth of Massachusetts.  The Commissioners are Antonio Blasi, Steven Joy, Percy Brown.

Spring River (Maine): The Spring River is a short stream in Township 16, MD, Hancock County, Maine, USA.  From the outflow of Narraguagus Lake ( ), the river runs 4.0 mi northeast to its confluence with the West Branch Narraguagus River.

Seboeis River: The Seboeis River is a river in Penobscot County, Maine.  The river is the outflow of Snowshoe Lake ( ) in Maine Township 7, Range 7, WELS; Snowshoe Lake is fed via a short stream from Grand Lake Seboeis.  The river runs 28.1 mi south — through White Horse Lake, Seboeis Deadwater, Upper Seboeis River Gorge, and Gagnon Flat — to its confluence with the East Branch of the Penobscot River in T.3 R.7 WELS.

Maalbeek: The Maelbeek or Maalbeek (] ) is a stream that runs through several municipalities in Brussels, including Etterbeek, Ixelles, St-Josse-ten-Noode, Schaerbeek.  It is a tributary of the Zenne, which it joins up in Schaerbeek, from its source located to the south near the Abbey of La Cambre.  The name "Maalbeek", (meaning "mill brook"), comes from the Dutch words "beek" (meaning "brook") and "maal" (meaning "to mill").  Molenbeek has a similar derivation.  It was vaulted in 1872, at which time there were 58 ponds along the stream.  Nowadays, only six are left: the ponds of the Abbey of La Cambre; of Ixelles (two); of Leopold Park; of Marie-Louise Square; and of Josaphat Park.

Little Bog River: The Little Bog River is a short stream in Hancock County, Maine.  From its source ( ) in Osborn, the river runs 5.4 mi south to its confluence with Mill Brook in Eastbrook.  Mill Brook flows west to Webb Pond.  Via Mill Brook, Webb Pond, and Webb Brook, the Little Bog River is part of the Union River watershed.

Pennypack Trail: The Pennypack Trail is a rail trail located in eastern Montgomery County, Pennsylvania in the United States.  The trail runs 5.4 mi from Rockledge north to Byberry Road near Bryn Athyn along the former alignment of SEPTA's Fox Chase-Newtown Line.  The Pennypack Trail is used for biking, hiking, jogging, and horseback riding.  The trail is maintained by the Montgomery County Division of Parks, Trails, & Historic Sites.

Billings Mill Brook: Billings Mill Brook (also known as Mill Brook or Billings Mill Creek) is a tributary of Tunkhannock Creek in Wyoming County, Pennsylvania, in the United States.  It is approximately 3.5 mi long and flows through Lemon Township and Tunkhannock Township.  The watershed of the stream has an area of 12.7 sqmi .  The stream has one named tributary, which is known as Kern Glen Creek.  The surficial geology in the vicinity of Billings Mill Brook mainly consists of Wisconsinan Till, alluvium, and several others.  A lake known as Lake Carey is in the stream's watershed.  A number of bridges have also been constructed over Billings Mill Brook.  The stream's watershed is designated as a Coldwater Fishery and a Migratory Fishery.

Little Narraguagus River: The Little Narraguagus River is a short stream in Maine.  From the outflow of Bear Pond ( ) in Maine Township 28, MD, Hancock County, the river runs 3.3 mi southeast and east to its confluence with the Narraguagus River in Beddington, Washington County.

Southwest Branch Indian River: The Southwest Branch Indian River is a short stream in Addison, Maine.  From its source ( ), the river runs about 3 mi east to its confluence with the Indian River.

Supporting paragraphs: Little Bog River Hancock County, Maine
Answer: Hancock County