Maps from 1630 to the present show how the city, once an 800-acre peninsula, became what it is today. I have always loved looking at old maps of Boston that show how the coast has changed over the past 400 years, as more and more “man-made lands” were created. I was talking about this over the weekend with some friends, and today National Geographic published an article, “How Boston got bigger, with some great maps illustrating the changes. This map, printed in 1895, was designed to celebrate a century of transformation of the coast in Boston.
That's a staggering amount, and that history of land construction is part of what makes Boston so vulnerable to rising sea levels today. These eight historical maps, selected by Garrett Dash Nelson, curator of Maps & Director of Geographic Scholarships at Boston Public Library's Leventhal Map & Education Center, provide snapshots of Boston's growth over time, documenting the city's ongoing and changing relationship with the sea. The push for publication in Boston was driven by the reduction of the water table to levels that potentially began to reveal many of the piles of wood, which remain preserved in anaerobic conditions, such as a situation similar to a water-based city like Venice, for example, but once water levels reveal them, it makes them very susceptible to rotting. As someone who is lucky (sarcastic) to work all over Boston, many of the older buildings have randomly spaced square hatches in the basement.
In 1850, the Bostonians began to fill the bubbling cauldron in earnest (the 1867 Coast Survey map above shows the partially filled bay). When the Puritans arrived in 1630, much of the land that underlies some of the oldest parts of Boston did not exist. 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”. In 1929, cracks began to form in the grand entrance of the Boston Public Library after leaks in a sewer pipe reduced the water level in that part of Back Bay, causing the tops of many of the structure's piles to rot.
One of the largest areas of artificial land in Boston is in and around the Back Bay neighborhood of the city. In fact, if you're standing anywhere in Boston on squared streets, it's very likely that you're on crowded ground. Back Bay encompassed the great tidal flats on the north side of Boston Neck, which connected Boston to the mainland. 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.
In 1986, the city established the Boston Groundwater Trust, which tracks water levels in the city through a network of publicly owned monitoring wells.