Portsmouth Harbor
Portsmouth Harbor is a bay at the mouth of the Piscataqua River , which forms the border between the states of New Hampshire ( Rockingham County ) and Maine ( York County ).
The entrance to the bay is monitored by the Whaleback , White Island, New Hampshire, and Fort Constitution lighthouses .
The most important town on Portsmouth Harbor is the city of Portsmouth (New Hampshire) .
Coordinates: 43 ° 4 ′ 33 ″ N , 70 ° 42 ′ 7 ″ W.