Uhhhhh, wow. I'm surprised that you havent figured this out. Unless you aint in the USA then i'd understand. BUT SERIOUSLY, C'MON. Here's the answer:
They put up a memorial to show respect to the soildeirs who died for our country protecting its rights, and from being taken from us and made a communistic country.
The purpose of the Vietnam Veterans Memorial was to honor all who had served, with a special tribute – their names engraved – for those who did not return.
The Vietnam Veterans Memorial stands as a symbol of America's honor and recognition of the men and women who served and sacrificed their lives in the Vietnam War. Inscribed on the black granite walls are the names of more than 58,000 men and women who gave their lives or remain missing.