“To appreciate why the Sebesteguk was of such importance in Indian communications we should note the topography of its drainage basin.”

http://tispaquin.blogspot.com/2009_08_01_archive.html

“The Sebesteguk fans out in wide-spreading branches. The longer but lesser branch, rising in Sangerville and Dover, was known as Maine Stream: the shorter and more important branch, with its chief head in Newport, was called the East Branch. Probably originally only the main river and its East Branch were known as Sebesteguk , “the almost through river”, because this was the shortest and easiest route to the Penobscot. The Reverend Paul Coffin, In his Missionary Journeys in Maine at the end of the 18th century, noted that it was but a mile overland from Penobscot to Kennebec rivers by the Sebesteguk and Sawadapskek. By following different tributaries, six important objectives could be reached.

Getting from the headwaters of the Sebasticook West Branch in north Dexter to Black Stream which flows into the Piscatiquis  which upstream begins at Moosehead Lake and downstream joins the Penobscot is a matter of less than a mile in the wet season. From the east Branch to several small connecting ponds that empty into the Kenduskeag  that joins the Penobscot near Bangor is a matter of a little over a mile . There is very little elevation separating the watersheds, just a wide wetland. For the native americans it was

1. by Twenty-mile Stream and Unity Pond to Belfast on Penob­scot Bay to get to Castine.
2. by Sawadapskek Stream to Hampden to strike any point on the lower tidal part of the Penobscot
3. by Kenduskeag Stream to Bangor, to reach any point near the head of tide
4. by Pushaw Lake to Old Town, entering the Penobscot above the falls section, for the routes to Machias and Croix.
5. by Main Stream to Piscataquis River for the upper Penob­scot and routes through to Mattawamkeag and Croix.
6. by Main Stream and upper Piscataquis waters to get to Moosehead Lake and Penobscot headwaters, keeping in a food and hunting country and avoiding the hard and dan­gerous route up the Kennebec.

Thus the Sebesteguk was a main highway of aboriginal travel and the principal route by which the French missions communi­cated with one another in the days when a mission was a palisaded town defending a strategic point in the French plan of occupying the country against the English.

p.12-13
 Indian place-names of the Penobscot valley and the Maine coast
 Fannie Hardy Eckstorm, Joseph Nicolar
 Printed at the University press, 1941 -  272 pages