The PSP originated as the Movimiento Pro-Independencia (MPI), founded on January 11, 1959, in the city of Mayagüez. The MPI was formed by a group of dissidents from the Puerto Rican Independence Party (PIP), former militants of the Nationalist Party of Puerto Rico and the Communist Party of Puerto Rico, and university students, some of them members of the Federación de Universitarios Pro Independencia (FUPI), including such figures as Lidia Barreto, Rafael Cancel Rodríguez, Loida Figueroa Mercado, Juan Mari Brás and Santiago Mari Pesquera, among others. The MPI was greatly influenced by the Cuban Revolution.