Blue Hill, Deer Isle & Stonington

The quiet coast of Penobscot Bay: from Blue Hill the route climbs Caterpillar Hill, crosses the 1939 Deer Isle–Sedgwick suspension bridge over Eggemoggin Reach, crosses Little Deer Isle and the causeway to Deer Isle, and rides ME-15 to the working harbor of Stonington at the end of the road. It comes back the same way to the bridge and closes the loop through Sedgwick and Blue Hill Falls. It's 50 miles. The bridge is narrow and high, so cross in single file, and ME-15 has little or no shoulder.

The Deer Isle–Sedgwick Bridge opened on June 19, 1939, and it's still the only road to Little Deer Isle and Deer Isle; before it, a ferry run by the same family for about 150 years crossed Eggemoggin Reach. It's a suspension bridge with a main span of 1,088 feet, high enough for sailboats to pass underneath. Soon after it opened it had wind problems like those of other bridges of its time, and it was stiffened with extra cable stays. In 2026 MaineDOT is studying how much service life the bridge has left and whether it will need replacing, and work on ME-15 in Deer Isle is planned for 2028.

The route reaches the bridge from Caterpillar Hill, a scenic turnout above the bay, and crosses Little Deer Isle and the causeway to Deer Isle. ME-15 runs on to Stonington, a working lobster harbor at the end of the road, and the route comes back the same way to the bridge before closing the loop through Sedgwick and Blue Hill Falls. The bridge is narrow and high and the descent to the south is steep, so cross in single file; ME-15 is narrow and winding with little or no shoulder.