Building the Back Bay: How Boston Filled a Bay and Planned a Neighborhood

The name gives it away. The Back Bay was once a tidal bay of the Charles River, a stretch of mud flats and shallow water behind the Boston peninsula. Within a few decades in the second half of the 1800s, it became one of the most carefully planned neighborhoods in America.

From mill dam to mud flat

In the early 1800s, a long dam was built across the bay to power mills, along the line of what is now Beacon Street. The dam cut off the tides, and the basin behind it filled with sewage and stagnant water. By the 1850s, the bay had become a health hazard, and the state and city agreed on a plan to fill it in.

Gravel by rail

Filling began in 1857. Trains carried gravel from pits in Needham, west of the city, running day and night. Crews dumped the fill and leveled it block by block, moving west from the Public Garden. The work continued for decades, gradually creating hundreds of acres of new land.

That is why Back Bay buildings rest on wooden pilings driven down through the fill. Those pilings need to stay wet to avoid rotting, and keeping groundwater at the right level is still a concern for property owners today.

A planned grid

Unlike the winding streets of older Boston, the Back Bay was laid out on a regular grid. The architect Arthur Gilman is credited with much of the plan, which drew on the boulevards of Paris.

• Commonwealth Avenue has a wide central mall lined with trees and statues, running from the Public Garden west toward Kenmore Square.
• Cross streets are alphabetical, from Arlington through Berkeley, Clarendon, Dartmouth, Exeter, Fairfield, Gloucester and Hereford.
• Alleys behind the houses kept service traffic and deliveries off the main streets.

Churches, libraries and towers

As the land was filled, institutions moved in. Copley Square became the neighborhood’s civic heart. Trinity Church, designed by H. H. Richardson and completed in 1877, is often listed among the most important buildings in American architecture. Across the square, the Boston Public Library’s McKim Building opened in the 1890s.

In the twentieth century, the Prudential Tower and the John Hancock Tower, now known by its address at 200 Clarendon Street, added a modern skyline. The Hancock’s mirrored glass reflects Trinity Church, putting old and new Boston in a single view.

Winter in the Back Bay

The Commonwealth Avenue Mall is a lovely winter walk, especially after a snowfall. Start at the Public Garden and head west, reading the statues along the way, including memorials to Alexander Hamilton, the abolitionist William Lloyd Garrison and the historian Samuel Eliot Morison. Newbury Street and Boylston Street are close by for a warm drink.

The Back Bay shows what Boston could do when it set out to build a neighborhood from scratch. Its brownstones and bowfronts look settled and permanent, but they stand on land that, not so long ago, was under water.