In the mid-1600s, this site was the focal point of a three-nation struggle for control of the Delaware River. Dutch military leaders recognized its strategic importance for controlling river traffic in 1651 and established a fort here. Swedish settlers from Fort Christina, now Wilmington, seized the fort in 1654 and renamed it Fort Trefaldighet, or Fort Trinity. A year later, Peter Stuyvesant, the governor of New Netherland, forced the fort's surrender to the Dutch. The fort remained in Dutch hands until the English assaulted and captured it in 1664, and its capture assured English control of the Delaware Valley. Archaeologists working on this site found remains of the fort's defensive works, and they also found what may be a grenade or cannon ball.