Linking the inner and outer harbor and extending eleven miles from downtown Boston is the Boston Harbor Islands national park area. The park is composed of thirty islands that range in size from less than an acre to 214 acres and together embrace 1,200 acres of land over an area of fifty square miles. For descriptive purposes, they can be grouped in four clusters:THE INNER HARBOR ISLANDS of Dorchester Bay are those closest to Boston and embraced by the long, thin arms of Moon and Long islands to the south and Deer Island to the northeast. THE QUINCY BAY ISLANDS are those lying in Quincy Bay as well as a cluster of three islands in the center of the harbor that range between the Outer Islands and the arm formed by Moon and Long islands. THE HINGHAM BAY ISLANDS include those that lie inside the semicircular Hingham Bay and the peninsula of World's End. THE OUTER HARBOR ISLANDS, sometimes called the Brewster's, are the eight windswept islands at the eastern edge of Boston Harbor between the main shipping channel and Broad Sound.  These islands, the easternmost of which is eleven miles from downtown Boston, exhibit different sizes, shapes, and features due to the severe impact of wind and water on them