How much of Boston's land is man-made?

The Shawmut Peninsula is the earthen promontory on which Boston, Massachusetts was built. The peninsula, which originally had an area of only 789 acres (3.19 km), more than twice the size due to land reclamation efforts that were a feature of Boston's history throughout the 19th century. A co-worker and I bet on how much of the modern city of Boston lies on land created in what used to be water. If you expand Copley Square and the BPL on this map, you can get an idea of how much Boston has changed.

These eight historical maps, selected by Garrett Dash Nelson, curator of Maps %26 Director of Geographic Scholarships at Boston Public Library's Leventhal Map %26 Education Center, provide snapshots of Boston's growth over time, documenting the city's ongoing and changing relationship with the sea. Boston's land-building wasn't just about the need for more space, writes author Nancy Seasholes in her wonderfully comprehensive book Gaining Ground. As we entered the 20th century, many more land reclamation projects were in Boston's future, including the filling of the South Bay, the creation of the Seaport district in south Boston, and the construction of Logan International Airport in East Boston. Although this project eliminated the wetland ecosystem that existed there at that time that would be impossible under modern environmental regulations, it was considered a great boon to the community for two reasons.

Bonner's map shows Boston sitting on a peninsula in technical terms, it's actually a “tied island” grounded by a sandy spit called “tombolo”. No American city had attempted a recovery on this scale when Boston in 1857, using Needham gravel, began to fill more than 600 acres of tidal basin, literally Back Bay. Filling the land behind tidal dams not only provided space for new neighborhoods, but also solved an urban planning challenge. I am pursuing a master's degree in science and my area of interest is a large wetland complex that was filled with mining waste and is currently leaching contaminated groundwater into the Clark Fork River.

The southern line was drawn from Cottage Farm Station (near Boston University) to a pumping station in Dorchester, and through an underwater channel to Moon Island. It's unclear whether letting dirt build up was part of their plan, but the new owners soon began pressuring the city to allow them to fill the pond and sell the land. Today, the 50 acres of new land in Mill Pond is known as the Bulfinch Triangle, after architect Charles Bulfinch's triangle-shaped plan for the new streets (visible on the 1826 map below). The extensive map collections of the Geography and Maps Division allow us to see how urban landscapes have evolved over time, whether through the forces of nature or human engineering.

Bryant Delosier
Bryant Delosier

Proud zombie buff. Wannabe pop culture specialist. Wannabe internet expert. Devoted bacon expert. Lifelong food enthusiast.