The Shawmut Peninsula: How Boston Tripled Its Size
On a cold March day in 1630, Governor John Winthrop stood on the deck of the Arbella and gazed at the Shawmut Peninsula—a compact landmass dominated by three steep hills, surrounded by tidal marshes and mudflats, connected to Roxbury by a narrow strip called Boston Neck that disappeared underwater at high tide. Within weeks, Winthrop and approximately 1,000 Puritan settlers had established the Massachusetts Bay Colony on this unpromising site. They named it Boston after the English town many of them had left behind. The settlement was precarious: fresh water was scarce, the land was rocky and difficult to farm, and the surrounding marshes bred disease. Yet within a generation, Boston had become the largest and wealthiest town in British North America.
What made Boston thrive was not its natural advantages—it had few—but its people's determination to remake their environment according to their vision. The original Shawmut Peninsula was dominated by three hills: Copp's Hill to the north, Beacon Hill in the center, and Fort Hill to the south. Trimountain, as the area was originally known, was steep, difficult to build on, and limited in space. As Boston's population grew—reaching 7,000 by 1690 and 16,000 by 1750—the need for more land became desperate. The solution was radical: cut down the hills and use the earth to fill in the surrounding tidal flats and marshes.
The first major project began in 1807 when the summit of Beacon Hill was lowered by sixty feet. The earth was loaded onto horse-drawn rail cars and dumped into the Charles River and nearby marshes, creating new buildable land. But the most ambitious project came after 1850: the filling of Back Bay. For centuries, the area west of Boston Common had been a tidal estuary—a 450-acre expanse of marshland that smelled foul at low tide and was considered a public health hazard. Beginning in 1857, a massive operation commenced to fill the entire bay. Gravel trains ran around the clock, bringing fill from Needham, nine miles away. Each train carried thirty-five carloads of gravel. Over thirty-five years, more than 450 acres of new land were created—the elegant neighborhood of Back Bay, with its grid of alphabetically-named streets (Arlington, Berkeley, Clarendon, Dartmouth) and fashionable brownstones.
