Question: What colony along the lower reaches of the Delaware River in North America from 1638 to 1655, featured the fortification and settlement of Fort Nya Elfsborg?

Context paragraphs:
Fort Nya Elfsborg: Fort Nya Elfsborg was a fortification and settlement established as a part of New Sweden.  Built in 1643 and named after the Älvsborg Fortress off Gothenburg, Fort Nya Elfsborg was located on the New Jersey side of the Delaware River, between present day Salem and Alloway Creek.

Naamans Creek: Naamans Creek (spelled Naaman Creek on federal maps) is a tributary of the Delaware River in northeast New Castle County, Delaware and southeast Delaware County, Pennsylvania The stream rises near the intersection of Foulk Road and Naamans Creek Road at in Bethel Township, Pennsylvania, flows through Arden, Delaware, and discharges into the Delaware River at in Claymont, Delaware.  The creek is believed to be named after a Minqua chief who befriended the Swedish settlers of the area.  A large tract of land along the creek was deeded to Governor Johan Risingh by chief Peminacka in 1655.

Fort Christina: Fort Christina (later renamed Fort Altena; Swedish: "Fort Kristina" ) was the first Swedish settlement in North America and the principal settlement of the New Sweden colony.  Built in 1638 and named after Queen Christina of Sweden, it was located approximately 1 mi (1.6 km) east of the present downtown Wilmington, Delaware, at the confluence of the Brandywine River and the Christina River, approximately 2 mi (3 km) upstream from the mouth of the Christina on the Delaware River.

New Sweden: New Sweden (Swedish: "Nya Sverige", Finnish: "Uusi Ruotsi" , Latin: "Nova Svecia" ) was a Swedish colony along the lower reaches of the Delaware River in North America from 1638 to 1655, established during the devastating Thirty Years' War while Sweden was a significant Northern European military power.  New Sweden was one part of Swedish colonization efforts in the Americas.

Delaware Valley: The Delaware Valley is the valley through which the Delaware River flows.  By extension, this toponym is commonly used to refer to Greater Philadelphia or Philadelphia metropolitan area ("the [Lower] Delaware Valley Metropolitan Area"), which straddles the Lower Delaware River just north of its estuary.  The Delaware Valley Metropolitan Area is located at the southern part of the Northeast megalopolis and as such, the Delaware Valley can be described as either a metropolitan statistical area (MSA), or as a broader combined statistical area (CSA).  The Delaware Valley Metropolitan Area is composed of several counties in southeastern Pennsylvania and southwestern New Jersey, one county in northern Delaware and one county in northeastern Maryland.  The MSA has a population of over 6 million, while the CSA has a population of over 7.1 million (as of the 2010 Census Bureau count).  Philadelphia, being the region's major commercial, cultural, and industrial center, wields a rather large sphere of influence that affects the counties that immediately surround it.

Fort DuPont State Park: Fort DuPont State Park is a Delaware state park located in Delaware City, Delaware.  Fort DuPont itself, named after Rear Admiral Samuel Francis duPont, was used as a military base from the Civil War through World War II, and was part of a three fort defense system, with Fort Delaware and Fort Mott with the purpose of protecting the Delaware River and the city of Philadelphia from naval attacks.  Fort DuPont State Park is situated along the Delaware River and Chesapeake and Delaware Canal.

Si River: The Si River () is a watercourse located in Shandong Province and, in ancient time, in Jiangsu Province, China.  It rises in the southern foothills of the Mengshan Mountains (蒙山) then flows through Sishui County, and the cities of Qufu and Yanzhou before emptying into Lake Nanyang (南阳湖).  In ancient times the river was a large tributary of the Huai River, converging with the waters of the Fan (反), Sui (睢), Tong (潼) and Yi (沂) and numerous other rivers then passing through present day Yutai County, Pei County, Xuzhou City, Suqian City and Siyang County in Shandong and Jiangsu Provinces.  At Sikou (泗口) (also known as Qingkou (清口), present day Huai'an City, Jiangsu), the Si River discharged into the Huai River.  From very early on the Si River was connected with the Huai and Yangtze Rivers as well as the Central Plain of China for a long period in its history.  In 1194, at the time of the Song and Jin Dynasties, the Yellow River altered its course southwards, engulfing the lower reaches of the Si River below Xuzhou City and those of the Huai River below Huai’an City.  As a result, the Si River no longer exists in Jiangsu Province.  In 1855, the Yellow River once more altered its course northwards.  However, due to the large amount of silt carried by the river, it left behind a 4 to high layer of mud in the lower reaches of the Si River’s former course.

Roaring Brook (Lackawanna River): Roaring Brook (also known as Roaring Branch Creek or Roaring Creek and historically known as Nay-aug) is a tributary of the Lackawanna River in Lackawanna County, Pennsylvania, in the United States.  It is approximately 21 mi long and flows through Covington Township, Madison Township, Moscow, Roaring Brook Township, Elmhurst Township, Dunmore, and Scranton.  The watershed of the stream has an area of 56.3 sqmi .  Its named tributaries include Little Roaring Brook, Rock Bottom Creek, White Oak Run, Van Brunt Creek, Bear Brook, and East Branch Roaring Brook.  It has a high level of water quality for much of its length.  However, it is affected by abandoned mining land, stormwater, and other impacts in its lower reaches.  Reservoirs in the watershed include the Hollister Reservoir, the Elmhurst Reservoir, and others.  The stream also flows through the Nay Aug Gorge and passes over the Nay Aug Falls, which are on the National Register of Geologic Landmarks.  It flows through a concrete channel in its lower reaches.  The topography of the watershed contains rolling hills in its upper reaches and the mountainous land of the Moosic Mountains in its lower reaches.

Swedes' Landing: Swedes' Landing is the warehouse road found along the Minquas Kill in Wilmington, Delaware that is close to the Delaware River.  This was the site where the initial Swedish landing took place and marks the spot where the New Sweden colony began.  The first Swedish expedition to North America, under the command of Peter Minuit, embarked from the port of Gothenburg in late 1637.  The members of the expedition, aboard the ships "Fogel Grip" and "Kalmar Nyckel", sailed into Delaware Bay, which lay within the territory claimed by the Dutch West India Company and anchored at a rocky point on Swedes' Landing on March 29, 1638.  They built a fort on the site which they named Fort Christina after Queen Christina of Sweden.

Kaskaskia River: The Kaskaskia River is a tributary of the Mississippi River, approximately 325 mi long, in central and southern Illinois in the United States.  The second largest river system within Illinois, it drains a rural area of farms, as well as rolling hills along river bottoms of hardwood forests in its lower reaches.  The lower reaches of the river have been canalized to allow barge traffic.

Supporting paragraphs: Fort Nya Elfsborg New Sweden
Answer: New Sweden