Age: 20
Occupation: Former Mexico border police chief
Previous TIME 100 appearances: 0
When Marisol Valles García stepped up last fall to be police chief in the town of Praxedis Guadalupe Guerrero on Mexico's violent northern border — her predecessor was beheaded by drug thugs — the slight, bespectacled criminology student and young mother was hailed as the bravest woman in Mexico. Now Valles, herself the target of death threats, has requested political asylum in the U.S. But her example has inspired more Mexicans to seek ways to confront their country's nightmarish narcobloodshed.