At an event centered on one of the darkest times in human history, more than 1,000 Holocaust survivors, World War II veterans and other dignitaries crowded into a tent to celebrate the 20th anniversary of the U.S. Holocaust Memorial Museum and filled it with the joyous sounds of laughter, some tears and Yiddish. Lots of Yiddish.

It was an emotional ceremony, but also celebratory for all that the museum has accomplished over the past two decades.

Former president Bill Clinton and Nobel Peace Prize laureate and Holocaust activist Elie Wiesel, who were at the dedication of the museum in 1993, returned Monday and reiterated the reason for its existence: that such genocide might “never again” occur.

Clinton said that many buildings in Washington hold meaning for visitors from around the world but that “the Holocaust Museum will be our conscience.”

People tend to dwell on the half of a percent of DNA that differentiates us from each other rather than the 99.5 percent of identical genes, a focus that allows us to justify discrimination in the pursuit of power, Clinton said.

“That makes us vulnerable to the fever, the sickness that the Nazis gave to the Germans,” Clinton said. “We see this virus taking form. . . . It is still the biggest threat to our children and grandchildren reaping the full promise of an interdependent world.”

The museum, a sprawling collection of more than 16,280 artifacts and 12,500 survivor testimonies, is a dedication to truth, Wiesel said. Nearly 35 million visitors have passed through its doors during the past 20 years.

The speeches by Clinton and Wiesel wound up a weekend of events that included panel discussions, workshops, family research projects and a concert. Also attending were the people who hid Jews and other minorities persecuted in 1940s Europe to keep them from being killed or sent to concentration camps.

Organizers said they chose to hold an anniversary celebration for the museum’s 20th year rather than its 25th because many survivors and veterans are in their 80s and 90s.

At a luncheon Monday, tables were divided into cities, countries, Nazi camps and other groups so survivors and veterans could reunite with old friends. During a dinner Sunday evening, the museum presented its highest honor, the Elie Wiesel Award, to World War II veterans. The award was accepted on their behalf by Gen. Dwight D. Eisenhower’s granddaughter Susan Eisenhower.

A second award was given to Polish politician and historian Wladyslaw Bartoszewski on behalf of all who rescued Jews during the Holocaust.

The museum also launched a $540 million campaign to invest in Holocaust research and global education outreach, acquire more artifacts, and create a new collections and conservation center, as well as to grow its endowment.

Katharina Skalina, a survivor of the Budapest Ghetto who now lives near Philadelphia, attended the ceremony Monday. She said she remembered the day that the Nazis occupied her city: March 19, 1944. She was in her early 20s during the occupation.

“It is very emotional to go through the museum . . . everything comes back,” Skalina, 88, said. “But it is a wonder to know there is a museum to remind people what was happening.”

Skalina, who moved to the United States with her husband and fellow Holocaust survivor Alexander in 1968, said the 20th anniversary marks a special occasion for an organization with a unique global role.

The museum “gives an education to let the world know that humanity is very important,” Skalina said.

Burton Miller, an Army veteran of World War II who served in Europe from 1942 to 1946, said he arrived at the Buchenwald concentration camp in Germany after it was liberated in 1945. The Loudoun County resident said the museum’s presentation of the era surprised him during his first visit years ago.

“I thought it would depict the horrors of the Holocaust . . . but it was in many ways an uplifting experience,” Miller, 89, said. “It does describe the horrors, but it also describes the resilience of the human spirit.”

Speakers at Monday’s ceremony urged younger generations to look to the future and preserve the heroes, victims and memories of the past. Lisa Zaid, whose grandfather led 97 people into the forests of Poland to escape deportation to the Treblinka extermination camp, told survivors and veterans that their lives would be honored.

“The forests of Poland will never tell this story,” Zaid, the granddaughter of four Holocaust survivors, said. “They will never remember the rich and vibrant lives of these individuals . . . but we have this museum.”