Organizers from ANSWER International and other peace groups called the "Emergency Troops Out Now Rally" in the wake of the killings of dozens of people at a mosque in Fallujah on Wednesday.
Demonstrations were also planned in New York and Los Angeles. Activists hoped 4,000 people would turn out but Chicago police estimated the crowd at just 150.
"I am tired of turning on the television set and seeing another five or ten Americans killed," Paul Watson told CLTV, a cable television news outlet.
Two U.S. Army soldiers and three Marines were killed in Iraq Friday. More than 45 have been killed in fighting with Iraqis this week.
Speakers called for the end to the U.S. occupation and withdrawal of 135,000 U.S. forces.
The demonstration was peaceful and no one was arrested.
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