to the north, the hooked Nantasket Peninsula and Point Allerton to the south, and the harbor islands in the middle. The harbor is often described as being split into an inner harbor and an outer harbor. The harbor itself comprises with of shoreline and 34 harbor islands. Inner harbor The inner harbor was historically the main port of Boston and is still the site of most of its port facilities as well as the Boston waterfront, which has been redeveloped for residential and recreational uses. The inner harbor extends from the mouths of the Charles River and the Mystic River, both of which empty into the harbor, to Logan International Airport and Castle Island, the latter now connected by land in 1928 to Boston, where the inner harbor meets the outer harbor. Outer harbor The outer harbor stretches to the south and east of the inner harbor. To its landward side, and moving in a counterclockwise direction, the harbor is made up of the three small bays of Dorchester Bay, Quincy Bay and Hingham Bay. To seaward, the two deep water anchorages of President Roads and Nantasket Roads are separated by Long Island. The outer harbor is fed by several rivers, including the Neponset River, the Weymouth Fore River, the Weymouth Back River and the Weir River. Dredged deepwater channels stretch from President Roads to the inner harbor, and from Nantasket Roads to the Weymouth Fore River and Hingham Bay via Hull Gut and West Gut. Some commercial port facilities are located in the Fore River area, an area which has a history of shipbuilding including the notable Fore River Shipyard. Land fill In the 1830s, members of the maritime community observed physical decay in the harbor. Islands in the outer harbor were visibly deteriorating and erosion was causing weathered materials and sediment to move from where it was protecting the harbor to where it would do the most harm. Recent shoaling experiences and comparisons with old charts caused observers to insist that the inner harbor was also filling and created widespread anxiety about the destruction of the Boston Harbor. Although the scientific understanding of hydraulics was still in its infancy and there were high degrees of uncertainty regarding the meeting of land and water, scientists and engineers began to describe the Boston Harbor as a series of channels created and maintained by the scouring force of water moving in