Under the gaudy neon lights of the most famous square in the world, the objects -- most of them seized from the store of a jailed Philadelphia art dealer -- were placed one by one on a conveyor belt before being dropped into the crusher to the sound of applause.
"Today's ivory crush serves as a stark reminder to the rest of the world that the United States will not tolerate wildlife crimes, especially against iconic and endangered animals," said US Secretary of the Interior Sally Jewell.
In just three years around 100,000 elephants were killed for their ivory, Jewell said.
She said there was a growing demand for ivory, with international organized crime networks seeing it as a low risk, high-profit market.
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Dozens of demonstrators held up posters in Times Square saying that 96 elephants fall victim to the illegal trade each day.
It was the second time that US authorities have staged a massive public destruction of ivory.
In November 2013, the US Fish and Wildlife Service, which comes under the department of the interior, organized the destruction of more than five tonnes of ivory in Denver.