Florida Keys National Marine Sanctuary protects about 2,900 square nautical miles of coastal and ocean waters from South Florida through the Keys to Dry Tortugas. Its boundaries include more than 1,700 islands, the Florida Reef, extensive mangrove forests, and seagrass fields, including the northern hemisphere’s largest documented contiguous seagrass community. Designated on December 28, 1990, as the nation’s ninth national marine sanctuary, it was created to protect the Keys’ marine resources while allowing compatible use. The area is significant both ecologically and culturally, preserving rich biodiversity and maritime heritage, but it faces continuing threats from development, overfishing, tourism impacts, warming seas, and invasive species.