"Si me matan...Yo sacaré mis brazos de la tumba y seré mas fuerte"
"If they kill me... I'll reach my arms out through my tomb and I'll be even stronger."
Further influenced by her uncle, Minerva became involved in the political movement against Trujillo, who served as the country's official president from 1930 to 1938 and from 1942 to 1952, but ruled from behind the scenes as a dictator from 1930 to his assassination in 1961. Minerva studied law and became a lawyer, but because she declined Trujillo's romantic advances in 1949, she was only allowed to earn a degree, but not have a license to practice law. Her sisters followed suit, first Maria Teresa, who joined after staying with Minerva and learning about their activities, and then Patria, who joined after witnessing a massacre by some of Trujillo's men while on a religious retreat. Dedé joined later, due to having been held back by her husband Jaimito.
They eventually formed a group called the Movement of the Fourteenth of June (named after the date of the massacre Patria witnessed), to oppose the Trujillo regime. They distributed pamphlets about the many people whom Trujillo had killed, and obtained materials for guns and bombs to use when they finally openly revolted. Within the group, the Mirabals called themselves Las Mariposas ("The Butterflies"), after Minerva's underground name.
Minerva and María Teresa were incarcerated but were never tortured due to mounting international opposition to Trujillo's regime. Three of the sisters' husbands (who were also involved in the underground activities) were incarcerated at La Victoria Penitentiary in Santo Domingo. Despite these setbacks, they persisted in fighting to end Trujillo's leadership
On 25 November 1960, Patria, Minerva and María Teresa, and their driver, Rufino de la Cruz, were visiting Patria and Minerva's incarcerated husbands. On the way home, they were stopped by Trujillo's henchmen. The sisters and the driver were separated and were clubbed to death. The bodies were then gathered and put in their Jeep where it was run off the mountain road to look like an accident.
In 1994, Dominican-American author Julia Álvarez published her novel In the Time of the Butterflies, a fictionalized account of the lives of the Mirabal sisters. Alvarez called the sisters "feminist icons" and "a reminder that we have our revolutionary heroines, our Che Guevaras, too". The novel was adapted into the 2001 movie of the same name. The movie starred Salma Hayek as Minerva, Edward James Olmos as Trujillo, and singer Marc Anthony in a supporting role.
On December 17, 1999, the United Nations General Assembly designated November 25 as the annual date of the International Day for the Elimination of Violence against Women in commemoration of the sisters. The day also marked the beginning of a 16-day period of Activism against Gender Violence. The end of the 16 days, on December 10th, is noted as International Human Rights Day.