SUBTITLE: The place where Vietnam memories are collected.
The Vietnam Veterans Memorial is located on the south end of the National Mall and receives around 3 million visitors each year.
When anyone leaves a memento, it travels 12 miles here, to the National Park Service's regional storage facility.
JANET DONLIN, NATIONAL PARK SERVICE MUSEUM TECHNICIAN: As we found the corner, this is where we store the Vietnam collection. There's over 1,400 boxes here. They're all organized by when they were left at the wall. So, it's all in chronological order and we've been collecting since 1982. I think there's probably anywhere between 250,000 and 400,000 objects.
SUBTITLE: The Vietnam Memorial is the only location on the Mall where items are saved for posterity.
DONLIN: This was actually a flag that was given to John George Sparks. He was a prisoner of war for five years in Vietnam. So, you can see here there's a cross and there's a little ribbon that kinds of holds the cross the place. It describes that this cross is made out of the toothpaste tube that — well, a toothpaste tube that he used in Vietnam, and the tie here comes from his POW uniform.
This was a letter that was left by possibly a wife of a POW. In two days, it will be 50 years since he became missing in action. All these years, I have loved you and believed that you were alive in a POW camp and would come home to us. But now, I am accepting that you are with the Lord and have been. I loved you then, Bruce, and I love you now and I always will love you.
This motorcycle was left at the walls, actually left at the Vietnam Veterans memorial. It was left in 1995 for Memorial Day. So, there's a group of veterans who got together. They got together in made this motorcycle in honor of the 37 men from Wisconsin who were MIA or POWs.
This is a retired plate in Wisconsin. No one else can put this on their motorcycle. It's not to be ridden on until all 37 are accounted for.
SUBTITLE: More than 1600 Americans remain unaccounted for from the Vietnam War.