Boston Harbor, a continuously working harbor since the mid 17th-century, and the islands have undergone significant physical transformation over the last 300 years. Both human actions and natural forces have caused this change. Many people are aware of the dramatic expansion of the Shawmut Peninsula  by filling tidal land over the centuries to create what is now the city of Boston. However, most people are not aware of similar changes to current and former harbor islands. Natural forces significantly eroded Sheep and Hangman islands to mere outcroppings. Causeways and land bridges were constructed to connect Worlds End, Deer, and Nut islands to the mainland, as well as other former islands such as the end of what is now a section of the town of Hull and the Castle Island extension in South Boston. A modern vehicle bridge was constructed for Long Island. Massive landfill connected Wood, Noddles, Apple, and Governors islands to form East Boston and Logan Airport. Today’s metamorphosis is the dramatic re-construction of Spectacle Island with material from the central artery highway tunnel through Boston known as the Big Dig. Today’s visitor to the islands may get the sense of permanence. However, people and nature have had a dramatic impact on the geography of this resource over a relatively short period of time.