rocky shoreline with green herbaceous plants hugging the upland on the near left side of the frame
A rocky shoreline on Calf Island, with green herbaceous plants hugging the upland on the near left side of the frame. Some of the plants have small yellow flowers. The rocks closest to the water are dark with seaweed and moisture from the outgoing tide. A flock of white shorebirds dot the far shore. Beyond the birds waves crash in big whitecaps on near shore rocks. Behind the rocks several islands rise above the horizon line.

NPS Photo/Vincent

A pinkish-brown rocky shoreline spattered with white bird droppings.
Calf Island. A pinkish-brown foreground of large boulders at the shoreline spattered with white bird droppings. The blue harbor water can be seen stretching between Calf Island and the Brewster Islands in the distance; the small white Boston light station tower rises atop Little Brewster Island.

NPS Photo/Vincent

Between the horn of Cape Ann to the north and the defiant, jutting arm of Cape Cod to the south and east, the Boston Harbor forms a giant crescent in the central coast of Massachusetts, and is the beating heart of the New England shoreline. The harbor sits within an ancient feature, known as the Boston Basin, which predates the formation of North America. Over the course of over 400 million years, it has seen tropical latitudes, multiple advances and recessions of the sea, and multiple periods of glaciation—the latter couple of which deposited and then carved many of the hills that currently dapple its surface. Today, within a vibrant metropolitan area, the Boston Harbor Islands provide a dynamic assembly of ecosystems, ranging from rocky, windswept shores to dense forests to developed and filled land—all with a long and complicated history of human use.

Stand at the dock and find a cloud of comb jellyfish drifting through the pilings; watch a double-crested cormorant drying its wings atop a navigational buoy; find trees that rise clear out of the asphalt—there are few places where the intersection of urban and coastal ecology are so well illustrated.


Explore the plants, animals, and landscapes of the islands.

a flat grassy upland is filled with staghorn sumac with winding branches and red leaflets.
Natural Features & Ecosystems

Discover Boston Harbor's vital ecological hotbed of rocky and sandy shores, salt marshes, sea grass beds, tidal mudflats, and more.

Last updated: November 18, 2021

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