The Sanibel Causeway is a causeway in Southwest Florida that spans San Carlos Bay, connecting Sanibel Island with the Florida mainland in Punta Rassa. The causeway consists of three separate two-lane bridge spans, and two-man-made causeway islands between them. The entire causeway facility is owned by Lee County and operated by the Lee County Dep…The Sanibel Causeway is a causeway in Southwest Florida that spans San Carlos Bay, connecting Sanibel Island with the Florida mainland in Punta Rassa. The causeway consists of three separate two-lane bridge spans, and two-man-made causeway islands between them. The entire causeway facility is owned by Lee County and operated by the Lee County Department of Transportation. The causeway is 3 miles long with a $6 toll for island-bound vehicles only.