The Ponce massacre was an event that took place on Palm Sunday, March 21, 1937, in Ponce, Puerto Rico, when a peaceful civilian march turned into a police shooting in which 19 civilians and two policemen were killed, and more than 200 civilians wounded. None of the civilians were armed and most of the dead were reportedly shot in their backs. The march had been organized by the Puerto Rican Nationalist Party to commemorate the abolition of slavery in Puerto Rico by the governing Spanish National Assembly in 1873, and to protest the U.S. government's imprisonment of the Party's leader, Pedro Albizu Campos, on sedition charges.