The majestic steel beams of a soaring office tower beginning to rise from the ruins of the World Trade Center are a tribute to American resilience, but also a marker in the decline of yet another industry. Not an inch of imported glass went into the two lost towers, built 40 years ago. The lower floors of the new one will soon be sheathed in Chinese glass.

The decline of glassmaking in America started gradually in the 1990s and accelerated during the Great Recession. What’s more, the big companies, like Corning and Guardian Industries, say that even as the economy improves, they are unlikely to bring domestic employment and production back to prerecession levels. Imports, for one thing, inhibit sales. And bigger profits lie abroad, so they are channeling investment and expansion to their overseas factories.

“Those who are looking through the rearview mirror, waiting for the glass industry in this country to come back, should know it isn’t going to come back, not the way it was,” Russell J. Ebeid, Guardian’s chairman, said in an interview.

With the nation’s unemployment rate hovering at 10 percent, the possibility of stemming job losses holds considerable appeal. So, in an argument likely to be repeated if unemployment persists at record high levels, some are pressing the Obama administration to offer protection for the nation’s glassworkers by raising existing tariffs on imported glass, particularly from China, as is happening on steel and tires. That action or something similar is supported by the United Steelworkers and also by many of the small manufacturers that operate more than 300 factories in this country.