The people have gathered in DuPont Circle at around 6 p.m. local time (22:00 GMT), more people are joining them as the vigil goes on.
The park in the historic district in Washington, DC is lit with candles that people are bringing with them. The rally is peaceful and there is no increased police presence. Some participants have given speeches, and named every victim of the tragic shooting.
A gunman opened fire on Saturday inside a synagogue, killing 11 people and injuring another six. He was wounded in a shootout with police before surrendering to security forces.
Authorities said they had charged the man and were treating the shooting as a hate crime. US President Donald Trump called it an act of anti-Semitism that will be confronted anywhere it appears.