Daughters for Sale: How Young American Girls Are Being Sold Online One woman estimates she had over 100 encounters in three weeks at age 15.

 -- In an old home movie, young Natalie is laughing and running around with a soccer ball. She’s around 12 years old, and she looks at the camera and says, “When I grow up, I would like to be a doctor.”

But a few years later, that laughing, carefree young girl was sold for sex allegedly through the website, Backpage.com. She estimates she was paid for sex over 100 times, and she firmly believes that the site made it possible for her pimp to post ads offering her for sex over and over again.

“Continuously. All day, every day. 24/7,” Natalie told ABC News “Nightline.” She has asked us to refer to her as “Natalie” for this report, and her parents have asked that we do not use their last name.

Natalie is now a 21-year-old mother with a toddler and another baby on the way. She is part of a major lawsuit against Backpage.com, the highly controversial online classifieds site that is currently being investigated by the U.S. Senate for its alleged connection to underage sex trafficking.

Sen. Claire McCaskill, D-Missouri, told “Nightline” that Backpage “requires more of someone who wants to sell a motorcycle than of someone who wants to sell a child.”

When Natalie was 15 years old, she said she made a decision she would regret for the rest of her life. She ran away from home because she said she received a bad grade at school and was nervous about how her parents would react to it.

“I thought maybe things would be easier if I could just go do it on my own,” she said. “I didn’t want them to… be disappointed… I had told all my friends that I was going to run away.”

Natalie said she ran across a soccer field, jumped a fence, found a bus stop and took a bus to downtown Seattle, where she met an older girl at a youth shelter.

“She was very familiar with the shelter and the Seattle area in general and she told me… we could go hang out,” Natalie said. “I had never smoked weed before, never drank… I don’t know. I was having a good time.”

Back at home, her mother Nacole found a letter Natalie had left behind. She called her husband Tom and said they needed to go to the police immediately.

“I was in shock,” Tom said. “You know, kind of just floored that-- Gone? Why? You know? Where? You know, how?”

Out on her own, Natalie quickly learned the dark side of life on the streets. She said her older friend was turning tricks right in front of her.

“We would walk on the highway and then people would come pick her up and I would sit in the back seat and then she would sleep with them,” she said. “A lot of them would ask if they could sleep with me and she would tell them ‘no,’ until a pimp picked us up and then took us to his house.”

That’s when Natalie said she was raped for the first time. She had been a virgin.

“After it happened he threw a towel at me and some carpet cleaner and told me to clean up the carpet because there was blood,” Natalie said. “That was pretty difficult. And then after that, they cut all my hair off and then put me in some really skimpy clothes and taught me how to walk in heels,” she continued. “I got really scared after that, and I ended up running out of there.”

Natalie said she sneaked out of the garage door and found a police officer who called her mother.

“I was definitely scared and I just wanted to go home. I was nervous,” she said.

Her family was overjoyed to have her back, but Natalie was still grappling with how to deal with what had happened to her.

“I didn’t know how to treat her. I didn’t know if she wanted me to hug her,” her father Tom said. “For the first time since the day she was born… It felt awkward to hold my own kid.”

At school, Natalie said word had gotten around what had happened to her, and she said she was bullied and called horrible names. This feeling of not belonging drove her to make another bad choice: she ran away a second time with the help of that older friend she had met in Seattle. Natalie was still just 15 years old.

“I ran down the street to the bus stop… and she was parked there waiting for me,” Natalie said.

Then she met 32-year-old Baruti Hopson. She said he was kind to her at first and gave her a place to stay, but then she said things took a horrible turn.

“I had started talking to him, confided in him a little bit about family life and just how stressed out I was,” she said. “He had asked me if I had ever worked before, and I told him, ‘briefly’ … I didn’t really know what I was doing.

“And then he told me that I wouldn’t be on the streets,” Natalie continued. “And I was like, ‘Well what does that mean?’ And he’s like, ‘Well I’m not going to have you walking the streets’ … And then that’s when Backpage came into play.”

Natalie said Hopson told her Backpage.com was “safer” and that it was easier “not to get caught.”

Backpage’s site is surprising simple, similar to Craigslist, but with a racy adult services section with categories like “Escorts” and “Body Rubs.” These are technically legal categories, but many in law enforcement say these ads are thinly veiled code for prostitution. While it is free for someone to post adult services ads, Backpage makes money by offering paid add-ons, including the ability to re-post the ad every hour and to post it in multiple neighboring cities.

“He put me in all these clothes, took some pretty provocative pictures of me and then got to Backpage, and then you can click on to post an ad,” she said. “He just showed me how to do it, so I could do it myself.”

Natalie said the website asked if she were 18 years or older, but “a simple yes click was about as far as that went.”

With Backpage ads posted with titles such as “Well worth it, 150 an hour” and “It won’t take long at all,” Natalie said she was working every single day and started earning as much as $4,000 a weekend, handing over all the cash to Hopson.

“He started getting physically abusive and really, I couldn’t even go in the bathroom without the door being unlocked,” Natalie said. “He would sleep in the living room next to the front door, so I couldn’t leave.”

Natalie's mother Nacole said she was shocked to learn there was a website where this could to happen to underage girls, like her daughter.

“I live in an American town, how can my kid be sold on the internet?” she said.

“When you hear that your 15-year-old child is posting an ad for sex or for rape in her case, and that she’s getting 25 to 30 calls an hour, and you’re thinking, ‘Well how many of these is she having to answer? I mean, there’s 24 hours in a day… how many times a day is my child being raped?” Nacole added.

But the sad truth is Nacole is among many American mothers who have had to ask themselves the same question.

A mother who’s asked us to call her "Debbie" said her teenage daughter, who we’re calling "Crystal," left home one night after an argument. It only took 48 hours of her being gone for Debbie to find her images on Backpage.

“I remember that she had on the see-through lacy teddy,” Debbie said. “And she’s 14.”

Crystal says that when she left home, she arranged to stay with a friend’s boyfriend’s mom. Instead of giving her a safe place to stay, she says this woman forced her into prostitution. Crystal says they were re-posting her Backpage ad every five minutes and forcing her to have sex with the men who would come to the house.

Crystal, who is now 19, told “Nightline,” “It’s hard being that young and being trapped in a room and not knowing if you’ll go home to your mom, or if you’ll come out of there alive.”

"Megan," another mother who asked us to use an assumed name, said her 15-year-old daughter was also sold for sex on Backpage. Her daughter, who we’re referring to as "Kim," says she went to a party hosted by a friend’s older boyfriend on her fifteenth birthday. It was fun at first, but then Kim said she was told she couldn’t leave and was forced to take racy photos to post on Backpage.

“I got a call from a friend of mine that said that I needed to check Backpage because she thinks that she had saw my daughter on Backpage,” Megan said. “So I checked, and sure enough, her ad was there.”

Megan said she called the police and told them she saw Kim on a Backpage ad, and that they needed to do something.

“I told them they had to go get her,” she said.

Both of these girls were eventually rescued by police. The adults who posted them to Backpage were convicted in court. Kim and Crystal are also suing Backpage, and they are also represented by Natalie’s lawyers, Erik Bauer and Jason Amala. Backpage denies these allegations and is fighting them in court.

But so far, every lawsuit filed by a trafficked underage girl against Backpage has been dismissed because of a law called the Communications Decency Act of 1996. The law protects Backpage, among others, from being held legally responsible for what users post on its website. Also called the CDA, the law shields websites or online publishers for information posted by third parties.

“If someone publishes a faulty motorcycle [ad on Backpage.com], the buyer of that motorcycle shouldn’t be able to sue Backpage merely for posting the ad, that doesn’t make sense,” said ABC News’ senior legal correspondent Sunny Hostin. “Interestingly, under the law, there is no difference between Backpage posting the advertisement for the faulty motorcycle and posting the advertisement for the underage girl being trafficked for sex.”

Backpage, which is based in Dallas, has repeatedly claimed that they are part of the solution, not the problem. The company told ABC News in a statement that it employs moderators who diligently screen ads to stop underage trafficking on its site. They added that they have voluntarily undertaken a multi-tiered "policing system to prohibit and report attempts at human exploitation and the advertisement of prostitution" that screens for words and phrases that might "suggest illegal activity" and that the company actively cooperates with law enforcement.

"While the experiences of children (and adults) who have been exploited are tragic and heartbreaking," Backpage told "Nightline" in a statement today. "The solution does not lie in making online service providers responsible for millions of posts by third-party users (in Backpage.com’s case, approximately 50 million posts per year presently) – the practical effect of which is inevitably highly restrictive censorship or the total banning of certain categories of online content so that online service providers are not in constant anxiety about potential liability for the one ad that slipped through their moderation systems."

But many in law enforcement have openly challenged these claims, including Cook County Sheriff Thomas Dart, who in 2015 successfully petitioned every major credit card company to cut ties with Backpage. The only available payment methods on the site now are Bitcoin or mail-in check.

Natalie’s father Tom says his daughter’s disappearance pushed him to the breaking point. He would spend days in the car, driving around Seattle, searching desperately for his missing girl. Until one night, he said things went too far.

“I was driving down where these people hang out, and it was pretty obvious to me that this was a pimp and a girl,” he said. “I saw this, and I just got infuriated seeing this guy and this gal and I just turned my truck at him and floored it.

But Tom didn't go through with it. “I had intended on hitting him,” he continued. “And I just figured, I’m going to get my daughter on the news, you know, um, and the way I’m going to do that is I’m going to kill this pimp, you know? I bought a fifth of good whiskey and I said, ‘I’m done.’ That was when I started drinking… I almost killed myself doing that.”

Then, on the 108th night Natalie was missing, her Backpage ad was targeted in a sting set up by the Seattle Vice Squad. One of their officers had posed as a client, and when she walked into his hotel room, he stopped her.

“He says, ‘I know who you are, Natalie,’ and I mean I can only imagine how big my eyes were when he said that,” Natalie said. “Instantly I saw hundreds of lights that seemed outside, just storms of cops outside.”

One of those officers was Bill Guyer, a longtime Vice detective who spends much of his time on Backpage trying to rescue trafficked girls like Natalie. He and Natalie instantly formed a special bond the night she was rescued.

“I remember meeting Det. Guyer, and he actually drove me to the jail, and he kind of relaxed me… almost reminded me of my dad,” Natalie said.

Det. Guyer met Natalie’s parents and started a relationship with them too. He then helped Natalie build up the courage to testify in the trial of Baruti Hopson, who was sentenced to 26 and a half years in prison for promoting the commercial sex abuse of a minor.

“I tell her and every other girl that even though they don’t want to go to court, I don’t want to go to court, but I’d like to get them to the point where they’re like, 'I can’t wait to get on the stand and point them out to you, that’s the piece of crap that did this to me,'” Guyer said.

Guyer and the rest of the Seattle Vice Squad agreed to let “Nightline” embed with them as they set up a sting through Backpage, the kind of operation that’s become commonplace in police departments across the country. "Nightline" first met with Det. Lincoln, who’s asked that we change his name because of his frequent undercover assignments.

Lincoln showed “Nightline” the ins and outs of posting on Backpage. Lincoln says there are many commonly-used terms that may flag to him and the other detectives that a girl on Backpage is underage, like “new in town” and “eager to please.” It’s a code he says he’s learned through experience tracking down underage girls listed on the site.

But “Nightline” wanted to see what would happen if a Backpage ad didn’t just use these coded terms and instead blatantly suggest an underage girl was part of the deal. Would the ad be flagged and taken down by Backpage’s moderators?

So Det. Lincoln posted an ad for an 18-year-old escort, adding in a line that said she had “a younger friend” who was available as well. Minutes after he posted the ad, calls and texts started streaming in. The ad was up and running.

The ad remained up for about 36 hours, leading to dozens of phone calls, texts and even an arrest captured on “Nightline’s” cameras. The ad was only taken down after "Nightline" sent an anonymous email to Backpage’s dedicated email address for suspected child trafficking. It took eight hours to receive a response, which said to contact the National Center for Missing and Exploited Children, or NCMEC. The ad was taken down shortly after Backpage’s email response was sent.

Backpage later told “Nightline” in a statement that even though they thought that the ad did not clearly advertise that a girl under 18 was involved, their moderators did take it down and they say they banned the account. They also reported the ad to NCMEC.

Yiota Souras, general counsel for NCMEC, said 73 percent of the reports they receive from the general public about suspected underage trafficking involve a Backpage post.

Souras told “Nightline” she is skeptical of Backpage’s claims that they are closely monitoring their site, and of their attorney Liz McDougall’s claim that Backpage is “online to fight human trafficking online.”

“I don't think you can be in the business of providing basically an online bazaar for escort ads that includes the purchase and sale of children for sex, and say that you are online to help fight the problem,” Souras said.

In March, the Senate voted to hold Backpage CEO Carl Ferrer in contempt of Congress after he failed to appear at a hearing about online sex trafficking conducted by the Senate Subcommittee for Permanent Investigations.

“It was a unanimous vote”, said Sen. Rob Portman. “First time in 21 years this has happened. It’s a big deal.”

When asked why to specifically include Backpage in a hearing on online trafficking, Sen. McCaskill replied, “Backpage is the major player in this space. Therefore they have to be investigated. That’s as complicated as the subject is.”

A circuit court is expected to rule on the contempt charge sometime in the coming months.

Backpage also refused to respond to the Senate Subcommittee’s subpoenas for internal company documents relating to how it moderates its adult services ads, and exactly how much money they’re making off of them. The Senate is now seeking to enforce the subpoena. The nearly 200-page Senate report is available for download here.

Despite this refusal, the Senate’s own investigators say they were able to obtain company emails from Backpage to its moderators. One email in the Senate report addresses underage ads specifically, and contains a line instructing moderators not to delete an ad unless they are “really very sure” the girl is underage. Other emails in the Senate report suggest Backpage was telling its moderators to simply edit out words and pictures from posts if they did not comply with Backpage’s terms of service. They are told to then post the edited ad anyway, even though the investigators say this editing would not change the nature of the underlying transition.

“We're talking about big money,” said Sen. Rob Portman, R-Ohio. “And we have evidence that leads us to believe that they have edited ads in order to keep their profitability.”

Backpage declined to comment on the Senate’s findings, but their lawyers are currently fighting the contempt charge in a D.C. court. The court will decide if Ferrer will be compelled to testify and if Backpage has to hand over their internal documents. In court filings, Backpage claims the Senate’s request is a violation of the First Amendment, because it “seeks every bit of information relating to every editorial decision made in the past six years.”

Backpage’s corporate group is projected to have a revenue of $173 million dollars this year alone, although they will not say what percentage of that comes from the adult ad section, according to documents from the Senate Subcommittee on Permanent Investigations.

“I'm betting that when we get all the financials they're not making much money selling motorcycles. But they're making a whole lot of money selling children,” said Sen. McCaskill. “I'm betting that's why they're working so hard at keeping this information out of the public eye.”

Backpage, which was owned by Village Voice media until 2012, was sold to an “unnamed Dutch holding company” in December 2014, according to news articles at the time. “Nightline” discovered that CEO Carl Ferrer had opened a business in the Netherlands, which seems to be running two escort ad-based websites called NakedCity.com and EvilEmpire.com, as well as a very similar version of Backpage called “Cracker.” It is available almost everywhere except the United States.

Ferrer declined “Nightline’s” repeated requests for interview, and when we tracked Ferrer to a classified ad industry conference in downtown Amsterdam, he again refused to speak with us.

“He is in Amsterdam… because he wants to avoid the bright light of attention that we are placing on his company,” McCaskill said. “I don't think Amsterdam is far enough for him to go to avoid that bright light.”

Back in the U.S., others, like Natalie and her family, are waiting for their day in court. Natalie is hoping her Washington state lawsuit, which focuses on the claim that Backpage knowingly developed itself into an online marketplace for illegal prostitution, will be the first of its kind to be successful against the company.

“To whoever owns Backpage, Carl Ferrer, whoever-- he’s got to go home at night and know that he’s selling kids today,” her father Tom said. “He’s just as accountable as the pimp that sold her, in my mind.”

Natalie’s attorney Erik Bauer said, “Reports of child sex trafficking have increased over the last five years due to the internet. According to the AIM Group, Backpage controls 80 percent of that market… this is a big business.” AIM Group is an interactive media and classified advertising consulting organization.

Backpage responded to the allegations laid out in the Washington state lawsuit, according to court documents, stating that, "Backpage does not allow advertisements on its website to contain naked images, images featuring transparent clothing, sexually explicit language, suggestions of an exchange of sex acts for money, or advertisements for illegal services. In addition to these rules, specifically for advertisements posted in the “escort” section of its website, Backpage does not allow any solicitation directly or in 'coded' fashion for any illegal service exchanging sexual favors for money or other valuable consideration, any material on the Site that exploits minors in any way, or any material ... that in any way constitutes or assists in human trafficking."

For Natalie, her horrific experience also has robbed her of a piece of her high school years.

“I’ve never been to a football game. A high school football game,” she said. “I’ve never had a prom. I’ve never been to homecoming, and I see all my pictures. All my friends’ pictures on Facebook, and they have all that. They have memories… It makes me a little bitter.”

But in all the sadness, one ray of light for Natalie has been the special relationship she and her parents have now with Det. Guyer.

“To this day, six years later, he calls me on my birthday. Every year,” she said. “I actually said he’s the godfather of my little girl.”

“He’s my hero,” Tom added. “He saved my little girl and brought her home.”

ABC News' Lauren Effron contributed to this report

If you suspect underage sex trafficking, please call 1-800-THE-LOST or visit missingkids.com.