This 1858 lighthouse is owned by the Coast Guard but is in a small section of Acadia National Park on the southwestern side of Mount Desert Island. Steps lead down to the outside of the Light or you can take steep stairs and scramble over rocks for a view from the other side. You might see whales or seals off the shore.
If you go:
Parking is free, though an Acadia National Park pass must be displayed. The small parking lot is open 9 a.m. to sunset. It is a steep ascent to both viewpoints, though the southern side is easier.
Links:

Lighthouse Rd
Bass Harbor, Maine 04653 USA
Mailing address:
Acadia National Park
PO Box 177
Bar Harbor, ME 04609 USA
Phone Numbers:
Acadia National Park
+1 (207) 288-3338
+1 (207) 288-3338