Sanibel is a city in Lee County, Florida, United States, on Sanibel Island. The population was 6,064 at the 2000 census, with an estimated 2006 population of 6,066. It is part of the Cape Coral–Fort Myers Metropolitan Statistical Area. The main town is at the eastern end of the island. The city was formed in 1974 as a direct result of the main causeway being built in 1963 to replace the ferry, and the rampant construction and development that occurred afterward.