Nearly 300,000 minors — the vast majority of them girls — were legally married in the United States between 2000 and 2018, according to a 2021 study. Child marriage is defined as any marriage where at least one of the parties is under the age of 18. It was legal in all 50 states until 2018. Ten states have since passed bans to end the practice.

The minimum marriage age has fluctuated over the centuries: In colonial America it was 12 for girls and 14 for boys — a reflection of English law at the time. The minimum ages remained in place unless specific states enacted laws to replace them.