Men, women and children placed wreaths on the granite base, which is inscribed with the names of Nazi death camps, concentration camps and ghettos.
"By standing here today," Mayor Nutter told the crowd, "we are affirming that we will never forget this tragedy because we will be the ones to remember to tell others."
The monument was created by Warsaw, Poland-born Nathan Rapoport, an internationally renowned sculptor who survived the war living in Russia. Rapoport also created the monument that was erected on the site of the Warsaw Ghetto, where the Nazis killed about 350,000 Jews.
Sarita Russ Gocial, 65, who chairs the committee that organizes the annual observance at the monument, has lived in Philadelphia since 1957. Born in Cuba to Holocaust survivors, she attended the unveiling in 1964.
"I remember it was a very important event," Gocial said. "My parents were very proud of it, and they gave a little bit of money for the monument because they were just getting established in this country."
Gocial said she has attended the event every year.
"It's important that we remember that 6 million Jews were killed systematically by the [German] government, and we need to make sure nothing like this ever happens again," she said.
Miriam Caine, 80, who attended yesterday's ceremony, recalled helping to raise funds for the monument.
"We collected anywhere from 25 cents to big dollars to make sure this monument would be finished," Caine said.
Caine was born in Bialystok, Poland, where her father owned a grain mill and textile factory. She was 7 years old in 1941 when she and her family were captured by the Soviets and sent to a Siberian labor camp for eight years, she said.
When Caine was 15, the family moved to Philadelphia.
"It's very important for young children to know that genocide can happen to anyone and it's still happening today," Caine said.
"The future generations must know, so that they will continue to tell our story, when we no longer can."