Miguel is a 15-year-old boy living in the impoverished village of San Jacinto, Mexico. He feels ill-suited for farm work and dreams of crossing the border to join his parents in California. Though he is intelligent and capable of taking charge, his resentment over his parents' long absence makes him quick to judge others, particularly his father and younger sister.

Elena is Miguel's 13-year-old sister, a pretty, dark-haired girl who is brave, stubborn, and highly capable of managing their grandmother's rancho. She desperately misses her mother and treasures the letters she receives from California. Despite Miguel's dismissive attitude toward her, Elena is clever and determined to forge her own path north.

Javi is an older, silver-haired migrant from El Salvador making his second attempt to cross the border. He previously worked on a coffee plantation until he lost his job, prompting him to leave his wife and children to find work in New York. Talkative and good-hearted, he demonstrates deep familial devotion and acts as a protective figure for younger travelers.

Abuelita is Miguel and Elena’s thin, gray-haired grandmother who has raised them for the past seven years. Though impoverished, she provides a nurturing, deeply moral, and devoutly Catholic home. She attempts to teach Miguel not to judge others harshly and offers him her treasured Virgen de Guadalupe medallion for protection.

Known by the nickname El Plomero, Moisés is an older man with green eyes and a mustache who works as a professional coyote. He is tough, stern, and uncompromising in his rules for survival. Driven by a deep respect for his former associate, he agrees to personally guide Miguel across the desert.

Papá is Miguel and Elena's father, who left his family in Mexico seven years ago to work as a field laborer in California. Self-taught after the fourth grade, he firmly believes education is the key to success and dreams of his children graduating from school. His personal pride sometimes complicates his efforts to reunite his family.

Mamá works alongside her husband as a field laborer in California. She maintains a strong connection with Elena through upbeat, newsy letters containing photos of the family, including the young twin daughters born in the United States. She represents hope and salvation to her teenage daughter in Mexico.

Don Clemente is San Jacinto's wealthiest citizen, driving a Mercedes and running a lucrative business smuggling people across the border. He is severely scarred on his left side from a tragic fire that claimed his family. He owes his life to Miguel's father and wishes to repay the debt by securing safe passage for the children.

Juanito is Don Clemente’s arrogant nephew. He enjoys a luxurious lifestyle funded by his uncle's business but lacks his uncle's sense of professional ethics. He is involved in drug trafficking and creates an immediate sense of distrust and rivalry with Miguel.

Chuy is one of Miguel's best friends in San Jacinto. He is a talented woodcarver whose family is dedicated to revitalizing their impoverished town through farming and tourism. He gifts Miguel his only valuable carving knife as a farewell present before the journey north.

Lalo is Miguel's close childhood friend who dreams of attending medical school in the capital. He gives Miguel his prized secondhand American soccer jersey before Miguel departs, asking his friend to promise they will reunite in ten years.

Colmillo is an acne-scarred teenage thief with a gold tooth who carries a gun. He targets vulnerable migrants sleeping near the border, using intimidation and violence to strip them of their money and valuables.

Capitán Morales is a self-important, corrupt federale who stops transport buses to extort travelers. He deports migrants who cannot pay his bribes, abusing his authority for personal financial gain.