The first destruction of ivory in the U.S. is now planned for November 14th.
Six tons will be crushed at the Rocky Mountain Arsenal National Wildlife Refuge, near Denver.

The crushing was previously suspended after the shutdown began on Oct. 1

The U.S. Fish and Wildlife Service will destroy government-held stockpile of ivory that it has compiled over the past 25 years.
The ivory to be destroyed includes full tusks, carved tusks, and hundreds of smaller carvings and other objects.

Some of the ivory was smuggled into the United States in large quantities; some was also intercepted on its way out of the country or as it was being unlawfully sold in interstate commerce. Some arrived in the U.S. without the appropriate Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) permits or was brought back by travelers who did not know (or did not follow) wildlife laws and regulations.

Here the official explanatory document from the U.S. Fish and Wildlife Service: http://www.fws.gov/le/pdf/OLE-Q-and-A-on-Ivory-Crush.pdf