Question: This census-designated place first settled in 1623 is home to a defensive fortification built at the mouth of what river?

full_context: Document 1: Kittery Point, Maine: Kittery Point is a census-designated place (CDP) in the town of Kittery, York County, Maine, United States. First settled in 1623, Kittery Point traces its history to the first seafarers who colonized the shore of what became Massachusetts Bay Colony and later the State of Maine. Located beside the Atlantic Ocean, it is home to Fort McClary State Historic Site, and Fort Foster Park on Gerrish Island. Cutts Island is home to Seapoint Beach and the Brave Boat Harbor Division of the Rachel Carson National Wildlife Refuge.
Document 2: Fort Point Light (Maine): The Fort Point Light, or Fort Point Light Station, is located in Fort Point State Park, in Stockton Springs, Maine. A lighthouse at this point has served as an active aid to navigation since 1835; the present lighthouse dates to 1857, and is listed on the National Register of Historic Places.
Document 3: York, Maine: York is a town in York County, Maine, United States, near the southern tip of the state. The population in the 2010 census was 12,529. Situated beside the Atlantic Ocean on the Gulf of Maine, York is a well-known summer resort town. It is home to three 18-hole golf clubs, four sandy beaches, and Mount Agamenticus. It includes the villages of York Village, York Harbor, York Beach and Cape Neddick.
Document 4: Fort McAllister: Fort McAllister was a Confederate earthen-work fort used to defend Savannah, Georgia during the American Civil War. It was the southernmost of the forts defending Savannah and was involved in the most battles. It was located on the Ogeechee River in Bryan County. It is listed on the National Register of Historic Places (#70000197). Fort McAllister was one of three forts protecting Savannah, the others being Fort Pulaski and Fort James Jackson standing in Confederate defiance of the Union naval blockade. The southeast coast of the United States was the place where both combatants tested the latest in naval artillery and coastal defenses. Fort McAllister was the key to unlocking the defenses around Savannah, one of the most important Confederate ports on the Atlantic Ocean.
Document 5: Fort McClary: Fort McClary is a former defensive fortification of the United States military located along the southern coast of Maine at Kittery Point. Built at the mouth of the Piscataqua River, it was used primarily throughout the 19th century to protect approaches to the harbor of Portsmouth, New Hampshire, and the U.S. naval shipyard.
Document 6: Fort Pickering: Fort Pickering is a 17th-century historic fort site on Winter Island in Salem, Massachusetts. Fort Pickering operated as a strategic coastal defense and military barracks for Salem Harbor during a variety of periods, serving as a fortification from the Anglo-Dutch Wars through World War II. Construction of the original fort began in 1643 and it saw use as a military installation into the 20th century. Fort Pickering is a First System fortification named for Colonel Timothy Pickering, adjutant general of the Continental Army and secretary of War in 1795. Today, the remains of the fort are open to the public as part of the Winter Island Maritime Park, operated by the City of Salem.
Document 7: Birch Point State Park: Birch Point State Park is a public recreation area occupying 62 acre on Penobscot Bay in the town of Owls Head, Knox County, Maine. The state park features a sandy, crescent-shaped "pocket beach" with scenic views of the Muscle Ridge Islands dotting Muscle Ridge Channel. The park is managed by the Maine Department of Agriculture, Conservation and Forestry.
Document 8: Fort Point State Park: Fort Point State Park is a public recreation area with historic features that overlooks Penobscot Bay from the easternmost tip of Cape Jellison in the town of Stockton Springs, Maine. The state park's 156 acre feature the Fort Point Light and the site of historic Fort Pownall. The park offers hiking trails, picnicking, and fishing.
Document 9: Seacoast Region (New Hampshire): The Seacoast Region is the southeast area of the U.S. state of New Hampshire that includes the eastern portion of Rockingham County and the southern portion of Strafford County. The region stretches 13 mi along the Atlantic Ocean from New Hampshire's border with Salisbury, Massachusetts to the Piscataqua River and New Hampshire's border with Kittery, Maine. The shoreline is generally very rocky and rough in nature, although a few sandy beaches have been created using jetties/groins, particularly in the towns of Rye and Hampton. The Seacoast Region stretches as far west as Epping. Portsmouth, the largest municipality and only city in Rockingham County, serves as the cultural and commercial hub of the region. Portsmouth has numerous historical landmarks and tourist attractions including Strawberry Banke, the Moffatt-Ladd House, the John Paul Jones House, and the Portsmouth Children's Museum, which moved to Dover in 2010. The Seacoast Region was the first area of the state to be permanently settled by Europeans in the early 17th century.
Document 10: Fort Halifax (Maine): Fort Halifax is a former British colonial outpost on the banks of the Sebasticook River, just above its mouth at the Kennebec River, in Winslow, Maine. Originally built as a wooden palisaded fort in 1754, during the French and Indian War, only a single blockhouse survives. A National Historic Landmark, it is the oldest blockhouse in the United States. It is now set in a municipal park, and is open to the public in the warmer months. It was the first of three significant forts which the British built on the major rivers in the Northeast to cut off the native water ways to the ocean (also see Fort Pownall and Fort Frederick (Saint John, New Brunswick)).
Document 11: Fort Knox (Maine): Fort Knox, now Fort Knox State Park or Fort Knox State Historic Site, is located on the western bank of the Penobscot River in the town of Prospect, Maine, about 5 mi from the mouth of the river. Built between 1844 and 1869, it was the first fort in Maine built entirely of granite; most previous forts used wood, earth, and stone. It is named after Major General Henry Knox, the first U.S. Secretary of War and Commander of Artillery during the American Revolutionary War, who at the end of his life lived not far away in Thomaston. The fort was designated a National Historic Landmark in 1970, as a virtually intact example of a mid-19th century granite coastal fortification. Fort Knox also serves as the entry site for the observation tower of the Penobscot Narrows Bridge that opened to the public on 19 May 2007.
Document 12: Fort McRee: Fort McRee, was a historic military fort constructed by the United States on the eastern tip of Perdido Key, to defend Pensacola and its important natural harbor. In the defense of Pensacola Bay, Fort McRee was accompanied by Fort Pickens, located across Pensacola Pass on Santa Rosa Island, and Fort Barrancas, located across Pensacola Bay on the grounds of what is now Naval Air Station (NAS) Pensacola. Fort Pickens was the largest of these. Very little remains of Fort McRee today.
Document 13: Fort Gorges: Fort Gorges is a former United States military fort built on Hog Island Ledge in Casco Bay, Maine. Built from 1858 to 1864, no battles were fought there and no troops were stationed there. Advancing military technology, including iron clad ships and long range guns, made the fort obsolete before it could be used. The fort is now a park, accessible only by boat. It was added to the National Register of Historic Places in 1973.
Document 14: Kennebunk, Maine: Kennebunk ( or ) is a town in York County, Maine, United States. The population was 10,798 at the 2010 census (The population does not include Kennebunkport, a separate town). Kennebunk is home to several beaches, the Rachel Carson National Wildlife Refuge, the 1799 Kennebunk Inn, many historic shipbuilders' homes, the Brick Store Museum and the Nature Conservancy Blueberry Barrens (known locally as the Blueberry Plains), with 1,500 acres (6 km²) of nature trails and blueberry fields.
Document 15: Yarmouth, Maine: Yarmouth is a town in Cumberland County, Maine, United States, located twelve miles north of the state's largest city, Portland. The town was settled in 1636 and incorporated in 1849. Its population was 8,349 in the 2010 census. As of 2015's estimation, this is about 0.6% of Maine's total population.
ground_truth: Piscataqua River