New Sweden (Swedish: Nya Sverige) was a Swedish colony along the lower reaches of the Delaware River in the United States from 1638 to 1655, established during the Thirty Years' War when Sweden was a great military power. New Sweden formed part of the Swedish efforts to colonize the Americas. Settlements were established on both sides of the Delaware Valley in the region of Delaware, New Jersey, Maryland, and Pennsylvania, often in places where Swedish traders had been visiting since about 1610. Fort Christina in Wilmington, Delaware, was the first settlement, named after the reigning Swedish monarch. The settlers were Swedes, Finns, and a number of Dutch. New Sweden was conquered by the Dutch Republic in 1655 during the Second Northern War and incorporated into the Dutch colony of New Net