The sizes of the islands in the park change every hour, as the ocean tides ebb and flow on their shores. All totaled, the park islands change from 1,483 to 3,067 acres during the tidal cycle. Learn how island acreage was measured, considering daily tides.
The names of several islands have also changed over time. How we selected the spelling of island names, and alternate names for some islands, are described in, "What's in a name?"
Choose an island below for details about each of the islands in the park. The topics shown are size, location, managing agency, facilities, natural history, historical sketch . . . and more.
Did You Know?
Boston Harbor Islands is one of 14 national park that has the word "islands" in the name. Other island parks include Channel Islands in California, Apostle Islands in Wisconsin, Governors Island in New York and Assateague Island in Maryland.