Police say the operation is tied to Chicago gangs.
Prosecutors say children as young as 12 were the victims of the sex trafficking operation conducted on Chicago's South and West sides.
The Illinois Safe Children act, which went into effect last year, enabled investigators to use court-ordered wire taps for the first time to investigate human trafficking. Through their investigation, they made disturbing discoveries as to how young women and girls are forced into the sex trade.
Cook County's top prosecutor was joined Wednesday by the Chicago Police superintendent and sheriff's police to announce a bust in a major human sex trafficking ring involving Chicago street gangs.
Nine people were arrested following a year-long undercover investigation into the trafficking of young women and children called Operation "Little Girl Lost."
"Gang members are not just selling drugs any longer, they are selling children and young women for sex right here in our own backyards," said Cook County State's Attorney Anita Alvarez.
Prosecutors say the suspects are a network of pimps that seduce girls, some as young as 12, to work in the sex trade, posting ads for their services on websites like Craigslist and Backpage.com, and arranging so-called "dates" with johns at various hotels on the South and West sides.
Four of the suspects appeared in court Wednesday and ordered held on bail, which in one case was $1 million.
"As for those who facilitated this criminal network, we will work to ensure that they cannot operate their business in such a manner in the future," said Chicago Police Superintendent Garry McCarthy.
Investigators say the suspects would use emotional and physical abuse to control the young women, in some cases driving around with them in the trunk of a car as punishment.
Investigators credit the use of wiretapping to help them crack the sex trafficking case, the first time a state agency has used such a tool.
"In a few instances, we actually have recorded instances of girls being beaten and abused and stuff like that, which was difficult to listen to," said Cook County Sheriff's Police Vice Unit Commander Mike Anton.
Investigators say they have been able to provide social services to dozens of girls to help them transition out of that life. They say the average age a girl becomes a sex worker is 13.
The other five people charged in this case appear in court Thursday.