More than 840 Holocaust survivors and some of the American soldiers who liberated them from Nazi death camps in World War II came together on Monday in what could be the last commemoration of its kind, the AFP news agency reported.

They gathered under a large white tent by the National Mall for a 20th anniversary tribute to the US Holocaust Memorial Museum, one of the most visited sites in Washington, with more than 1.6 million visitors a year.

Returning to the institution he dedicated in 1993, former president Bill Clinton said that “the Holocaust Memorial will be our conscience … for now and forever.”

With most Holocaust survivors and World War II veterans in their 80s or 90s, the museum opted not to wait until the usual 25th anniversary milestone to reassemble as many living witnesses to that dark period of history as possible, AFP reported.

Although it gets part of its funding from the US government, the museum hopes to raise
$540 million by 2018 to continue its work.

Honored guests Monday included more than 100 US military veterans, some wearing their carefully preserved wartime uniforms, from units that liberated Nazi death camps as Allied forces swept through Europe.

The event also paid tribute to Marc Toureille, who as a young boy in the Herault department of southern France, helped his pastor father Pierre-Charles Toureille to spirit hundreds of Jews to safety in Spain and Switzerland.

Living in a railroad village deep inside Vichy France “we didn’t know about the gas chambers, but we knew it would turn bad,” 84-year-old Toureille, who now lives in Massachusetts, told AFP.

Nobel Peace Prize laureate Elie Wiesel, 84, the museum’s founding chairman and a survivor of the Auschwitz concentration camp in Poland, appealed to younger generations never to forget.

“It is your memory that inherits ours,” he said. “Our memory will live in yours. Remember that, young people, that you have an ideal … the ideal of saving whatever the past has to offer for the future.”