Philly Shipyard Inc. and Matson Inc. marked a ship construction milestone, with a "dock mounting ceremony," Thursday in the construction of the first of two container ships that will be completed in the third quarter of 2018.

The South Philadelphia shipyard won contracts, valued at $418 million, in 2013 to build two 850-foot long containerships that will carry a mix of cargo for Matson Navigation of Honolulu between the West Coast and Hawaii.

The ships will be the largest container ships ever built in the United States, capable of moving 3,600 20-foot containers at speeds greater than 23 knots.

The first vessel is named for the late Hawaii Sen. Daniel. K Inouye, a long-standing supporter of the U.S. maritime industry.

The ceremony Thursday was in the dry dock, where the first engine room section weighing 420 metric tons, was lowered into place. Senior executives of Philly Shipyard and Matson placed coins under the section as part of a ship building tradition to bring good fortune and safe travels.