The country is waiting on a decision that will affect many countries.
Congress returns to Washington this week after its summer recess. House and Senate leaders will debate whether to back President Obama’s call for military strikes in Syria.
Demonstrators want lawmakers to know what they think.
People on both sides rallied Sunday in northern California.
The President wants Congress to approve a targeted military strike against the Assad regime. He said he believes evidence indicates the government used chemical weapons to kill more than 1,400 people.
The President plans to address the nation Tuesday night to push Congress to back him.