Boston Harbor’s drumlin islands, carved by glaciers and now partly submerged, form a unique park filled with wildlife, history, and scenic landscapes. Each island offers a mix of natural beauty and remnants of Boston’s storied past.
Around 20,000 years ago, during the height of the Wisconsin Glaciation, a massive ice sheet, more than a mile thick in some areas, covered the region that is now Boston Harbor. As the climate warmed, the glacier gradually melted and retreated, leaving behind long, streamlined hills of sediment and glacial debris known as drumlins. Over time, rising sea levels flooded many of these features, turning them into islands. This process created the only partially submerged drumlin field in North America, and one of just three such formations known worldwide.
Birth of the Boston Harbor Islands
Today, many of these drumlin islands and peninsulas form the core of the Boston Harbor Islands National and State Park. The park protects a unique mix of geological formations, historical landmarks, and natural ecosystems. On July 19, 2024, the Operational Land Imager (OLI) aboard NASA’s Landsat 8 satellite captured a detailed image (above) of these islands and the surrounding harbor.
The park includes 34 islands and peninsulas, but only four are reachable by car: Deer Island, Nut Island, World’s End, and Webb Memorial. Four others—Spectacle Island, Georges Island, Peddocks Island, and Thompson Island—are served by seasonal ferries, while several more can be accessed by private boat. Oversight of the park is coordinated by the Boston Harbor Islands Partnership, a federally authorized group made up of eleven agencies.
Rich and Varied Ecosystems
The islands host a wide variety of ecosystems, including salt marshes, sandy beaches, seagrass beds, tidal pools, mudflats, grasslands, and hardwood forests. The surrounding waters are home to lobsters, crabs, clams, and fish such as striped bass, bluefish, and flounder. In the intertidal zones, mussels and barnacles thrive, while the land supports numerous species of mammals, birds, reptiles, and amphibians.
Many of the islands have signs of human activity and history, from campgrounds, education centers, and homes, to former military infrastructure, fields, and health facilities. Long Island, for instance, was once connected to Boston via a highway bridge and contains aging government buildings, a performing arts center, fire station, chapel, crematorium, and other structures. (The bridge was closed in 2014.) Peddocks Island, one of the largest, has privately owned cottages on its western end and the remains of a coastal fort.
Beacon of the Harbor: Boston Light
Little Brewster Island hosts Boston Light, the oldest continually operated light station in the United States. While the lighthouse initially used tallow candles when it was built in 1716, kerosene was used starting in 1913. Today, two 1,000-watt electric light bulbs produce a 1.8 million-candlepower white light.
Georges Island and Fort Warren
Nearby Georges Island houses the remains of Fort Warren, a bastion-style fort built in the shape of a pentagon between the 1830s and 1860s. The fort was named after Revolutionary War hero Joseph Warren, the man who sent Paul Revere on his famous “Midnight Ride” before the Battles of Lexington and Concord. During the Civil War, the fort was used as a prison for Confederate officers and government officials, including Confederate Vice President Alexander Stephens. The fort was mostly constructed of granite blocks sourced from nearby quarries in Quincy and Cape Ann.
Long Wharf: Boston’s Maritime Hub
Farther west lies Long Wharf, a historically significant wharf at the base of today’s State Street that once served as a hub for Boston’s maritime trade. When it first opened in the 1720s, the wharf extended half a mile into the harbor, allowing up to 50 vessels to dock at once. Boston’s ports have evolved over the decades and centuries, with container cargo and cruise ships now arriving at terminals in South Boston and recreational boats docking at a marina on Long Wharf.
NASA Earth Observatory image by Wanmei Liang, using Landsat data from the U.S. Geological Survey.
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