US classifieds website Backpage.com has become one of the primary destinations on the internet to buy sex. Hundreds of advertisements are posted each day by both pimps and prostitutes.
With the advent of the internet, prostitution moved off the street and onto the web, presenting a new set of challenges for law enforcement and sex abuse watchdogs.
In the past several years, the newspaper company that owns Backpage, Village Voice Media, has faced a string of protests from activists, as well as lawsuits from victims of sexual exploitation who allege that the site aids and abets forced prostitution.
Village Voice Media declined to be interviewed for the story. In a statement to the BBC, it said it is acting legally and cooperating with authorities to help prosecute those who misuse the website.
The BBC's Matt Danzico spoke to individuals who sell themselves on the site and to those campaigning for its closure.