Early records indicate this protected inlet was called Eastern Harbor, a name that evolved into East Harbor. In 1868 the railroad needed track—Provincetown’s flourishing fish industry needed transportation and eventually the railroad brought fish directly from the piers to Boston and New York City. But laying the track meant creating a dike and closing off the inlet, which was then renamed Pilgrim Lake.
Although once a thriving salt marsh ecosystem, no native salt marsh vegetation was left after almost 140 years of impoundment. Instead, the floodplain was taken over by a non-native cattail species and some highly invasive plants.
“An oxygen depletion and fish kill in September 2001 prompted the Town of Truro and Cape Cod National Seashore to investigate options for restoring the East Harbor system through the drainage pipe. “In hopes of restoring some tidal exchange and improving water quality, the Seashore and the Town opened the clapper valves, and they have remained open continuously since November 2002. Despite limits on tidal exchange imposed by the pipe’s small diameter, and the distance that it travels underground, we have observed an impressive response in the recovery of salinity and estuarine biota.” (https://www.nps.gov/caco/learn/nature/east-harbor-tidal-restoration-project-page.htm)