The colony of New Sweden extended along the western bank of the Delaware River between what became Philadelphia and New Castle, Delaware. This map of New Sweden is attributed to Swedish engineer Peter Lindestrom in 1654, a year before the colony was conquered by the Dutch.
The area that became Philadelphia lies in the top center of this map. Among the points of interest marked is Fort Trefaldighet. Originally established by the Dutch as Fort Casimir, this fortification in modern New Castle, Delaware, was taken over by the Swedish led by Johan Risingh in 1654. They renamed the fort Trefaldighet, the Swedish word for Trinity, after Trinity Sunday, the day the fort was captured. On September 11, 1655, the Dutch retook Trefaldighet. The colony collapsed four days later when the Dutch captured Fort Christina, the main Swedish fort in what is now Wilmington, Delaware.