TWENTY thousand years ago, the glaciers that formed Long Island retreated. The sand that covered the shores of what became Port Washington had a mixture of grain sizes and shapes, different from that typically found along the Island’s Atlantic shoreline. Because of this quality, it packed together easily, and was well suited for making concrete. Years later, an industry grew.

Sand mining sprung up in Port Washington in the 1870’s, when New York City’s subways, skyscrapers, highways and bridges were first being built. The concrete of New York’s infrastructure and buildings — including the Chrysler Building, the Empire State Building, the World Trade Center, the Queensborough Bridge, the F.D.R. Drive and the West Side Highway — contain some of the 140 million cubic yards of Port Washington sand mined over the years.

There were sand mines in Oyster Bay, North Port and Huntington, all part of a local industry that at its height supported dozens of companies, among them Colonial Sand and Stone, Metropolitan Sand and McCormack Sand, and thousands of miners. But Port Washington, with the largest sandbank east of the Mississippi River and easy barge access to New York City, New Jersey and Connecticut, was the center of the business.