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It's a moment of "unprecedented attention" for child marriage around the world. Those words come from a 2016 Human Rights Watch report, which estimated that one in three girls in the developing world marries before the age of 18. The topic has slowly moved to the front burner of the global development agenda, and the United Nations has set a goal of eliminating child marriage by the year 2030.

But as the issue of child marriage gains visibility around the world, many Americans remain unaware of the problem in their own backyards, activist Fraidy Reiss told CBS News.

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"We cannot solve the child marriage problem globally if we don't first solve it here in the United States," said Reiss, the founder and executive director of the organization Unchained at Last.

Reiss's nonprofit helps girls and women plan their escape from forced marriages and rebuild their lives after the fact. The organization mainly focuses on providing pro bono legal support, including divorce litigation, custody battles, and restraining orders. But the organization also supports girls and women in other areas: from helping clients secure housing after their escape, to taking them to stressful appointments with lawyers and doctors, to connecting them to therapists, English classes, financial assistance in emergencies, and more.

Child marriage is legal in some circumstances in almost every state in the U.S. Though nearly every state has laws barring children under 18 from marrying, there are ways to get exemptions -- for example, by asking for judicial consent or presenting parents' permission, according to the Pew Research Center.

In 27 states, the law does not specify any minimum age below which a child cannot marry, according to Unchained At Last.

Helping children in forced marriages is murky territory for activists and social workers. A child who leaves home under the age of 18 is considered a runaway, meaning that social service organizations and shelters could face legal action for helping them.

Generally, children cannot initiate legal action in their own name. In many states, that means a child is allowed to marry but not allowed to divorce.

For Reiss, her work is deeply personal. Raised in an insular Orthodox Jewish community in Brooklyn, Reiss was forced at 19 into an arranged marriage which quickly became abusive. Under Orthodox Jewish law, only men have the right to grant a divorce.

Fifteen years into her marriage, Reiss divorced her husband, was granted a restraining order and full custody of their two daughters, and started a radically new chapter outside the community she was raised in. To this day, her family considers her "dead," she said.

"There's nothing easy about escaping a forced marriage," Reiss said.

National forced marriage statistics are hard to come by. In a survey of marriage licenses compiled by Unchained At Last, at least 167,000 children under 18 were married in the U.S. between 2000 and 2010. (That number is likely on the conservative side, as Unchained At Last could obtain age data from only 38 U.S. states.)

The vast majority of those children were girls married off to adult men, Reiss said.

Child marriage is most common in the southern United States, according to the Pew Research Center. It's most common in West Virginia and Texas, followed by states like Oklahoma, Arkansas, Tennessee, North Carolina, Nevada and California.

When it comes to child marriage laws, the U.S. in comparable to countries like Iran, Saudi Arabia and Yemen, Reiss said. Her organization is lobbying legislators across the country to restrict marriage to those 18 and older.

In some states, the movement has momentum. Bills to end or limit child marriage are currently pending in California, Connecticut, Massachusetts, Missouri, New York, Texas and Pennsylvania. In New Jersey, a bill to stop all marriage before age 18 has already passed the state's Assembly and Senate, and awaits a signature from Governor Chris Christie.

"Americans tend to think of marriage as a beautiful, happy, romantic thing," Reiss said. "It's important to know that marriage before 18 is not romantic and beautiful and happy. It is something ugly."