With more freedom to discuss the history of the camps, Auschwitz evolved into a more historically accurate account to include the Jews as Auschwitz's primary victims and other details of the mass murder.

That passage of time allows memorials and museums built amid fierce political debate to include other views. As gay people started fighting for their civil rights and gay issues rose to the forefront of the national debate, Holocaust memorial museums responded to demands that gay victims of the Holocaust be included in the accounting of the victims by including references in their exhibitions.

The fight by African-American descendants of slaves to make sure slavery is fully represented in history has also changed the way Southern memorials are presented. Historians and descendants of free and slave families who lived and worked on Southern plantations, along with emerging archaeological and historical records, are helping to tell a more complete story at South Carolina's historical sites, including Redcliffe Plantation State Historic Site in Beech Island, said Dawn Dawson-House, spokeswoman for the South Carolina Department of Parks, Recreation and Tourism.

"Redcliffe was once described as the former home of South Carolina Gov. James Henry Hammond, who supported South Carolina's secession and was widely known as the statesman who yelled 'Cotton is King' during a session of the U.S. Senate," said Dawson-House. "It's now interpreted as the governor's home, the home of three generations of his descendants and numerous African-American families like the Henleys, Goodwins and Wigfalls who worked at the site as slaves and later free men and women."

Enforcing appropriate behavior

As time passes and people who lived through a tragedy aren't around to remind viewers of their losses and enforce decorum, it can get harder for memorial staff to enforce appropriate behavior at sites honoring the dead.

Visitors to the Pearl Harbor memorials are asked to maintain a respectful atmosphere. The 1.4 million annual visitors to Auschwitz are expected to behave with "appropriate solemnity and respect" and follow a series of other rules designed to protect the reputation of the site's victims and the grounds.

"The site demands respect," said Pawe? Sawicki, a spokesman for Auschwitz. "When you walk in the authentic area with the fences, watchtowers visible, when you see the ruins of gas chambers, or prisoner barracks, you generally do not act disrespectful. That seems to be the huge power of authenticity."

Yet time can dull the sense of tragedy. Two cruises organized to commemorate the ill-fated Titanic journey had their solemn moments of memorial, but there was also lots of dining and fun scheduled during those trips. And perhaps the people heading to Nova Scotia to visit the Maritime Museum of the Atlantic and cemeteries filled with the Titanic dead can be forgiven for confusing fact with fiction. Dublin-born Joseph Dawson, 23, worked on board and was buried at Fairview Lawn Cemetery in Halifax. His tombstone gets flowers brought by fans of Jack Dawson, the character played by Leonardo DiCaprio.

(Whatever draws visitors, organizers of Nova Scotia events marking the recent 100th anniversary say their respectful tributes to the Titanic tragedy and the permanent collection of Titanic artifacts help educate visitors about the real loss of life that day.)

And certainly the culture of a particular place can take over. New York City is known as the city that never sleeps, and business certainly doesn't. It didn't take long after the World Trade Center fires were put out for small-time vendors to sell mass-produced $5 T-shirts and photos of the heroics at ground zero.

While some of that selling still goes on around the site, maintaining a tone of respect is much easier now that the memorial is built, said Daniels, the memorial president. "It's almost impossible for someone to step onto Memorial Plaza and not have a sense of their breath being taken away."

Daniels knows future generation won't have the intense memories of Sept. 11 that makes the memorial all the more powerful. "That makes our job even more important, when people don't have a direct connection," he said.

"It's our responsibility to make people understand what happened on this site, not just the tragic parts, but the coming together aspects. That goes to the second prong of our mission: building a museum that will deeply explore 9/11 -- a place where people can come and learn."

A new focus on life

When lawyer Daniel Eisenstadt visited Auschwitz many years ago, he was struck by the anonymity of the Jews who died there. To him, Auschwitz was "the ultimate posthumous victory for Adolf Hitler," he said. "All the people visiting knew about the people who were killed was the anonymity of the people who were killed. It was very much in line with Hitler's basic line about the Jews."

Eisenstadt and friend Fred Schwartz wanted to focus on the lives of the people who died. Their wish to provide context for the rich and diverse Polish Catholic and Jewish pre-war community surrounding the camps turned into the Auschwitz Jewish Center Foundation, which opened in 2000 in a renovated former synagogue in the old city center of O?wi?cim, a few kilometers from the camp.

Now a subsidiary of the Museum of Jewish Heritage in New York, the center educates international visitors, Polish school children and even visiting U.S. military officers studying genocide about the rich life of the Jewish community beyond the genocide.

"There is a trend in memorials to incorporate life itself, not just how people were killed but how they lived," said Eisenstadt, who served as the center's first executive director for three years and is now a board member.

That's also happening at the September 11 Memorial, according to Daniels. He's glad that people celebrate New York with a Broadway show and visit to the Statue of Liberty along with a visit to the memorial. Even as people pay tribute to the victims of 9/11, New York is thriving in and around the 16-acre site where the towers once stood.