It happened at about 6:30 p.m. Monday night at Pottawattomie Park in Rogers Park, police said.
Police said a man approached and invited the girl to his home in exchange for money. A person nearby intervened and helped the girl into the park's fieldhouse, where 911 was called.
Anyone with information is asked to contact Area 3 Bureau of Detectives at (312) 744-8200 and anonymous tips can be submitted to TIPSOFT.COM Reference - RD# JG253121.
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