People under the age of 18 cannot legally buy a beer in this country, or enlist in the military (without parental consent), vote in an election, buy a handgun or enter into a contract. But in some states, they can be charged with a crime as adults and, if convicted, sent to an adult prison.

A century ago, most states established juvenile courts, which focused less on punishment and more on treatment and rehabilitation. But over the years, more and more states began trying juveniles in adult courts.