WASHINGTON — Most Americans think of child marriage as a vestige of a bygone era. And yet in every state, people under 18 are allowed to marry.

Some states set minimum ages for brides and grooms — sometimes as low as 13 or 14 — and usually require the permission of a parent, judge, or both before a minor can wed. But laws in about half the states allow children of any age to marry, as long as they receive the proper permission.

That may be changing. This year legislators in 10 states have introduced bills to raise the marriage age. Proponents say updating marriage laws, which in many states are more than a century old, will help protect children from being pushed into marriages by parents and predators. Some lawmakers, disturbed by instances of pregnant girls heading to the courthouse to marry older men, argue that marriage licenses should not be given to men who have committed statutory rape.

Child marriages represent a small share of total marriages in the U.S., but still number in the tens of thousands. Nearly 60,000 15- to 17-year-olds were in marriages in 2014.

Those who marry as children face a unique set of potential legal complications, particularly if they want to leave the marriage.

In some states, people under 18 are not permitted to get divorced. Most domestic violence shelters won’t accept people under 18. And because they are legally still children, those who try to escape a marriage may be returned by social services to the parents who approved the marriage in the first place.

Trevicia Williams said she was 14 when her mother picked her up from school and took her to a Houston courthouse to marry a 26-year-old man. Her husband was the nephew of the head of the church her family attended and had recently gotten out of prison.

“It was my mom’s way of getting rid of me, to be honest, of getting rid of her problems. She saw the responsibility of raising children to be so overwhelming,” Williams, 47, said. “When he hit me the first time I called my mom and asked if I could come home and she said, ‘No.’”

Williams is pushing for a bill passed by the Texas Senate this month that would bar people under 18 from getting married, except for those who are emancipated, or given adult status, by a court.