The spire is divided into 18 sections that weigh between five tonnes and more than 67 tonnes. Eight of the sections are being transported via barge from Canada on the Atlantic Salvor.
It left Quebec on Nov. 16 and is expected next week at Port Newark in New Jersey.
The remaining sections are expected to arrive via truck in mid-December.
The Port Authority of New York and New Jersey, which owns the World Trade Center site, says progress of the barge and the spire can be tracked online: http://bit.ly/UWwvio.
Once the 125-metre spire is installed, the tower will stand 541 metres tall, making it the tallest in the Western Hemisphere. The Port Authority says it will take about three months to install.