About 130 protesters were arrested at an Occupy Chicago demonstration early on Sunday after they set up tents and refused to leave a public park after closing time, police said.
The protests, which have spread across the United States and to other countries since starting in New York last month, focus on anger over inequality of wealth, government bailouts of big banks and persistently high unemployment.
The breakup of the protest in Grant Park was the second mass arrest of Occupy Chicago demonstrators in the past week. A week ago, about 175 protesters were arrested.
The protesters were charged with violating a city ordinance, the equivalent of the lowest misdemeanor, and most were released after agreeing to appear in court, Chicago Police Officer Robert Perez said.