Yes, the three islands that make up the Sanibel Causeway—known as Causeway Island A, B, and C—are entirely man-made. They were created during the original construction of the causeway in the early 1960s using fill material dredged from the surrounding San Carlos Bay. These islands were designed to support the bridge spans that connect the Florida mainland to Sanibel Island. Over the decades, these islands have become incredibly popular recreational spots, serving as "public beaches" where visitors can park directly on the sand, fish, and launch kayaks. In 2026, following the devastating impacts of Hurricane Ian in late 2022, the islands have undergone significant reconstruction and "hardening" to protect the roadway from future storm surges. While they look like natural parts of the coastal landscape, they are engineering feats that serve as both a vital transportation link and a unique park system, providing some of the most accessible "drive-on" beach experiences in Southwest Florida.