The two routes continue into Blue Hill, where SR 15 turns northward, while 176 goes to the east.

SR 15 continues towards Bangor, straddling the east side of the Penobscot River, along with US-1A to the west.

SR 15 enters Brewer and follows South Main Street to an interchange with Interstate 395 (I-395) at exit 4.

Routes 6 and 15 remain concurrent for the better part of about 60 miles (97 km), traveling north to Moosehead Lake, and turning west to the small town of Jackman.

Within the towns connected by State Route 15, the highway also is known by various local names: When originally designated in 1926, SR 15 ran between Ellsworth and Greenville Junction.

In 1946, the route was truncated to Blue Hill, but, in 1963, it was extended south to its current terminus in Stonington.