Police say Nelson is witnessing the results of sophisticated human trafficking now run by gangs who've realized it's often easier and more profitable to move girls than it is to move drugs.
Authorities have many troubling stories to tell of the ways in which the girls are abused and victimized.
"People have been gang raped, tied up in Saran Wrap," Nelson said. "We're talking about 13-year-old girls left for dead in their hotel rooms without water or food for days. Pimps put logos on their bodies and they're treated like animals."
Geiger said Portland is badly in need of more shelters to help give the teen prostitutes a safe gateway off the streets.
"Often they end up in a juvenile detention center with less resources than they deserve," he said.
More often than not, Nelson said, the girls return to the street.
Escaping the Life
Katie was able to escape her pimp after waiting weeks for a bed in a shelter.
Roberts' daughter is no longer working as a prostitute, she said. But the young woman remains fearful that her pimp will find her.
Alston, who now works at a restaurant, said she hopes the family profession stops with her. She plans to shelter her curly-haired daughter, who she said has her hazel eyes, as much as possible.
"I want her to be successful and happy,'' she said. "I just want her to have everything I didn't."
Watch the investigation tonight on "World News" at 6:30 p.m. ET and more on "Nightline" at 11:35 p.m. ET