The group called Invisible Children hopes world leaders will take action to rescue children who have been abducted and forced to fight in Uganda's civil war.
"We are asking for somebody to come and stand up. This is an issue that needs to be confronted. We need something to be done about it. We're going to do something," said Melody Gates with the Invisible Children program.
The event was one of 100 that took place in ten countries around the world.
Many of the teens at Crissy Field filled out petitions pleading with the U.S. lawmakers to take action.
The civil war in Uganda started 23 years ago and has threatened two million innocent civilians.