Portland to Camden — lighthouses, Route 1 and the Farnsworth
Start at Portland Head Light in Fort Williams Park, Cape Elizabeth — the postcard Maine lighthouse, and the grounds are free to walk. Go early; the light is best before the tour buses. Back in Portland, grab a coffee in the Old Port and pick up I-295 north to Brunswick, then join Route 1 at Bath. In September the Wiscasset bridge bottleneck is mild on a weekday; if the line at Red's Eats is long, Sprague's Lobster across the street serves a comparable roll with a shorter wait (verify current hours — both are seasonal).
Continue up Route 1 to Rockland. Spend 90 minutes at the Farnsworth Art Museum (three generations of Wyeths, plus Louise Nevelson), then walk the Rockland Breakwater — seven-eighths of a mile of granite blocks out to the lighthouse, flat but uneven, about 45 minutes round trip. Skip it in fog or big swell.
Fifteen minutes north to Camden. Check in, then walk the harbor: the schooner fleet is still in the water in September and the light on Penobscot Bay is at its best around 6 pm. Dinner in town — September evenings fill up, so reserve earlier in the day. If you have energy, the short walk along Bay View Street past the yacht club is the local's after-dinner stroll.