Fort Caroline was a French settlement established in 1564 near the mouth of the St. Johns River in present-day Florida. It was founded by Jean Ribault as part of France's efforts to explore and colonize the New World. The fort served as a base for French expeditions and aimed to promote trade and spread Protestantism. In 1565, the Spanish, led by Pedro Menéndez de Avilés, attacked and captured Fort Caroline, renaming it San Mateo. This marked a significant moment in the struggle between France and Spain for control of North America. The fort's capture ultimately led to the decline of French influence in the region.