Hundreds of relatives and friends of the 16 victims gathered for ceremonies at Mississippi Valley State University and the nearby memorial, The Greenwood Commonwealth reported .
The special forces Marines on board the KC-130T military transport plane were going from North Carolina to California for training when it crashed July 10, 2017. The aircraft was flown by a New York-based Marine Reserve unit and known by the call sign Yanky 72.
"Your loss has become our loss," Mississippi Gov. Phil Bryant told those who came from as far away as Ireland for the ceremony.
Following the service, the crowd was driven in buses to witness the unveiling of the nearby memorial, which displays an image of a KC-130T plane set in granite and surrounded in a circle by the engraved names of the fallen.
About 30 people then set off on a 900-mile (1,450-kilometer) relay to Marine Corps Special Operations Command at Camp Lejeune, North Carolina.
Teams of marchers will be on the road around the clock for weeks, relaying rucksacks of dirt and sand from the crash site and memorial site over 900 miles to Camp Lejeune. They intend to plant a tree in the soil at Marine Corps Special Operations Command.
No cause for the plane crash has been released, as the investigation continues.
Cindy Elliott said the observance has helped her family with closure following the death of her son, 30-year-old Capt. Sean E. Elliott of Orange, California.
"We are grateful for the whole memorial, and we will never, ever forget them," she said of the victims.
Information from: The Greenwood Commonwealth, http://www.gwcommonwealth.com