The first time "Katie" danced at a strip club, she was 13, and in the seventh grade.
Not long before, the Oregon girl had gone on an ordinary outing to a mall in downtown Portland. She met some boys there and they invited her to a party in the suburbs. At the party, Katie met an older boy she would begin to date.
"He bought me a lot of things, like shoes, outfits and purses and stuff like that," said Katie, of J, who she began to think of as her boyfriend.
Before long, J told her he was having financial trouble, and he asked her if she would she dance, "just once," at a strip club, she said. Katie, who had only ever worn high heels to church and on special occasions, soon was forced into working as a stripper and a street prostitute six days a week, she said.
Every year, at least 100,000 children are forced into prostitution in the United States, according to the National Center for Missing and Exploited Children. And Portland, routinely voted one of the most livable cities in the country, hides a dark secret: It is a national hub for child sex trafficking, police and victims' advocates say.
Children, young teens from all over the country, but mostly from the small towns of the Northwest, walk Portland's streets.
Katie's inauguration into the life was like that of countless other girls.
That first day at the strip club, she remembers looking out from the stage.
"It was gross," she told ABC News. "They're like older than my dad and grandpap and I just wanted to go home. "
She was told, "You can't go home, you have to finish your shift," she recalled. "And I was like, 'I don't work here,' and they were like, 'You do now.'"
"I realized I pretty much walked into a trap," she said.
Katie's is a classic case, said Sgt. Mike Geiger, who heads Portland's sexual assault detail. Cute young girls are being targeted by pimps.
"They look for them in the malls, the parks, on MySpace, Facebook," Geiger said. "(A)nd they look for them in the schools and walking downtown. They strike up a friendship with them."
Pimps fish for girls whose home lives are lacking in some way.
If a girl indicates she's not getting enough attention or is having some other problems at home, "They will use the information and become their rescuer,'' said Geiger of the pimps' strategy. "'I can fix all that,' the pimps will say. 'I can give you a place to stay. You're way too mature to be treated like that.'"
The pimp will then give the girl clothes and other things, as well as affection, said Geiger. "And then the trap has sprung."
Ruth Roberts says that's what happened to her daughter.
"I was a single mom working really late ... making six figures,'' she said. "My daughter was getting A's and B's. Playing basketball. ... She had a good life, a good family, she didn't need anything."
But Roberts' daughter, then 16, met a guy on Portland's subway system. They "dated" and he convinced to her run away and live with him, Roberts said.
Soon, said Roberts, "She was walking the streets."
Forced to stroll Portland's notorious prostitution area around 82nd Avenue, referred to as "the track," even in the bitter cold.
Often, though, according to Roberts, her daughter was "rented" out on Craigslist.com.