Two decades ago, five of Massachusetts’ port cities simultaneously launched urban design and redevelopment plans for their waterfronts, creating innovative frameworks for public and private reinvestment. The ports had long suffered from the steady decline of maritime trade and traditional fishing industries, resulting in extensive deterioration of their harbors. But significant development pressure was beginning to build along the water’s edge. In Boston, landmark projects such as the World Trade Center and Rowes Wharf had captured the public’s eye, evoking the promise of new access and the investment value of our historic ports.

In Massachusetts, coastal edges are subject to a unique set of legal and regulatory requirements, collectively called Chapter 91. Special plans were needed in 1997 to create a consistent set of requirements where municipal and state jurisdictions overlapped. The resulting municipal harbor plans proved to be pivotal, changing the course for thousands of acres of land and the harbors that serve them.

Boston’s harbor planning unlocked the new mixed-use developments and remarkable public amenities that have transformed Boston’s urban waterfront. Dense redevelopment stretches along every district that rims Boston Harbor. A constantly growing network of walks, parks, boat landings, civic institutions, and programmed places has accompanied each increment of development. The waterfront hosts the Institute for Contemporary Art in South Boston, new public spaces and activities around the Fort Point Channel, community boating programs in East Boston, and much more. Less apparent are the environmental shifts. The Deer Island treatment plant removed sewer outfalls from Boston Harbor when it went into full operation in 2000. Healthy sea life is returning. We may need a new rock anthem to replace the familiar refrain in “Dirty Water.”

Because of the environmental, physical, and regulatory challenges they face, urban waterfronts are terrifically expensive to develop. Boston’s waterfront was well positioned, with billions in public investment followed by a runaway real estate market. The other port cities have their own stories to tell; development on the whole is proceeding, albeit more slowly.

The plan for Fall River, for example, recognized that outmoded highway infrastructure effectively blocked fruitful waterfront redevelopment. Since that time, an Interstate highway interchange and other roadways have been entirely rebuilt. The final step in freeing the waterfront from the highway is under way, leading to emerging opportunities for transformative development.

Gloucester has adjusted its harbor edges to invite recreation and public access, and remains in active pursuit of ways to retain its identity as a commercial fishing port, even within a regulated industry with an uncertain future.

After two decades fostering ideas for game changing uses that did not pan out, New Bedford has chosen to build upon its strategic location as a fishing port and venue for innovative, marine-dependent uses. This port is creating new public access and amenities, while setting the stage for a path-breaking 21st-century version of a water-dependent, entrepreneurial, industrial, and employment center.

Salem’s outdated energy plant dominated land and views along its harbor 20 years ago. An entrepreneurial venture has removed that plant and is replacing it with a compact natural gas powered facility that will be a better neighbor to the historic waterfront. Also benefiting will be the cruise ship wharf and public landing, which will be among the responsibilities of its newly formed Port Authority.

The moral of this tale is clear: Wise infrastructure investment leads to renewed waterfronts. Peering into the decades ahead, infrastructure investments must adapt our ports to climate change. There is still a lot to do.