The crosses by some names on the Vietnam Veterans Memorial in Washington, D.C., represent servicemen who are missing and unaccounted for, according to TheWall-USA.com. When a diamond appears by a name on the Vietnam Veterans Memorial, it indicates that the serviceman was killed in action.
The Vietnam Veterans Memorial was built to serve as a memorial to all those servicemen who served in the Vietnam War, both living and dead. The memorial, commonly called "The Wall," lists the names of more than 58,270 servicemen who died or were declared missing or prisoners of war as a result of the war. The memorial was designed by Maya Lin and completed in 1982. The wall receives approximately 3 million visitors each year, many of whom leave various sentimental items. These are collected by the National Park Service, which catalogs and stores all non-perishable items at the NPS Museum and Resource Center.