Question: USS Oscar Austin was built by the Maine shipyard located on what river?

Context paragraphs:
Portsmouth Naval Shipyard Museum: The Portsmouth Naval Shipyard Museum and the associated Lightship Museum are located on the downtown Portsmouth, Virginia, United States waterfront.  The museum covers the 250+ year relationship with the shipyard - America's oldest and largest naval shipyard located on the Portsmouth Waterfront.  The city and the shipyard have been intertwined since the founding of the Gosport Shipyard in 1767, which was later renamed Norfolk Navy Yard and finally Norfolk Naval Shipyard.  This rich history is told through exhibits, hands-on programs and special events.

Portsmouth Naval Shipyard: The Portsmouth Naval Shipyard (PNS), often called the Portsmouth Navy Yard, is a United States Navy shipyard located in Kittery on the southern boundary of Maine near the city of Portsmouth, New Hampshire.  PNS is tasked with the overhaul, repair, and modernization of US Navy submarines.  The facility is sometimes confused with the Norfolk Naval Shipyard in Portsmouth, Virginia.

Mykolayiv Shipyard: Shipyard named after 61 Communards (Ukrainian: Суднобудівний завод імені 61 комунара "61 Kommunar yard") is a major shipyard located in Mykolaiv, Ukraine.  In modern times, the shipyard has been most commonly referred to as Nikolaev North Shipyard.

Bath Iron Works: Bath Iron Works (BIW) is a major United States shipyard located on the Kennebec River in Bath, Maine.  Since its founding in 1884 (as Bath Iron Works, Limited), BIW has built private, commercial and military vessels, most of which have been ordered by the United States Navy.  The shipyard has built and sometimes designed battleships, frigates, cruisers and destroyers, including the "Arleigh Burke" class , which are currently among the world's most advanced surface warships.

Río Santiago Shipyard: The Rio Santiago Shipyard is a shipyard located in the city of Ensenada, Buenos Aires Province at the shores of the Santiago River.  It has been one of the major active and important shipyards in Latin America.  Founded in 1953, it has realized diverse functions in the naval, industrial and railroad sectors.  In its golden age the shipyard reached 8,000 workers on double shift.  In 2008 relies on 2,700 workers.

USS Oscar Austin: USS "Oscar Austin" (DDG-79) is an "Arleigh Burke"-class destroyer in the United States Navy.  "Oscar Austin" is named for Medal of Honor and Purple Heart recipient Private First Class Oscar P. Austin.  This ship is the 29th destroyer of its class.  USS "Oscar Austin" was the 17th ship of this class to be built by Bath Iron Works in Bath, Maine, and construction began on 9 October 1997.  She was launched and christened on 7 November 1998.  On 19 August 2000 she was commissioned at Bath, Maine.  The ship is currently part of Destroyer Squadron 26.

Brooklyn Navy Yard: The United States Navy Yard, also known as the Brooklyn Navy Yard and the New York Naval Shipyard (NYNS), was a shipyard located in Brooklyn, New York, east of the Battery on the East River in Wallabout Basin, a semicircular bend of the river across from Corlears Hook in Manhattan.  It was bounded by Navy Street and Flushing and Kent Avenues, and at the height of its production of warships for the United States Navy, it covered over 200 acre .  The tremendous efforts of its 70,000 workers during World War II earned the yard the nickname "The Can-Do Shipyard."

Johnson's Shipyard: Johnson's Shipyard, also known as Johnson's Tyne Foundry Shipyard was an engineering company and shipyard located in Normanby Road, South Melbourne, Australia.

Philly Shipyard: Philly Shipyard, formerly Aker Philadelphia Shipyard, is a commercial shipyard located in Philadelphia, Pennsylvania, United States on part of the site of the Philadelphia Naval Shipyard.  The commercial yard began after the United States Navy had ended most of its operations at the site.

Vuosaari shipyard: Vuosaari shipyard was a shipyard located in the district of Vuosaari in Helsinki, Finland.  Built by the Finnish state-owned company Valmet Oy in the early 1970s, the shipyard delivered 33 newbuildings and participated in building around 100 other vessels before it was closed in 1987 following the bankruptcy of Wärtsilä Marine.  Later, the longest dry dock in Finland was used by various ship repair companies until the construction of the new Vuosaari harbour cut the connection to the sea in 2004.  Despite various plans to re-use the old dry dock, now located inside the harbour perimeter, it remained without use until the basin was backfilled in 2015–2016.

Supporting paragraphs: USS Oscar Austin Bath Iron Works
Answer: Kennebec River