Tinicum Township, more popularly known as "Tinicum Island" or "The Island", is a census-designated place and township in Delaware County, Pennsylvania, United States. The population was 4,353 at the 2000 census. Included within the township‍ '​s boundaries are the communities of Essington and Lester. One of the island's notable aspects is the John Heinz National Wildlife Refuge at Tinicum, attracting visitors to the island year-round.