On March 21, 1937, a peaceful Palm Sunday march in Ponce, Puerto Rico, turns deadly when National Guard and Insular Police, under the direct military command of the U.S.-appointed governor of Puerto Rico, General Blanton Winship, open fire on the crowd killing 18 people, including a 7‑year-old girl. The Puerto Rican Nationalist Party organized the march to commemorate the ending of slavery in Puerto Rico by the governing Spanish National Assembly in 1873 and to protest the imprisonment, by the U.S. government, of Nationalist leader Pedro Albizu Campos on alleged sedition charges.
On March 21, 1960, South African police open fire on a group of unarmed black South African demonstrators, killing 69 and wounding 180 in the Sharpeville Massacre.