January – February – March – April – May – June – July – August – September – October – November – December
- March 1, 1954 - Four Puerto Rican nationalists attack the U.S. Capitol in protest of Puerto Rico's new Commonwealth status. 5 U.S. Representatives are injured.
- March 1, 1958 - Westernbank was founded.
- March 2, 1917 - The Jones Act is signed into law, granting U.S. citizenship to all Puerto Ricans and revised the system of government.
- March 2, 1940 - Birth of Tony Croatto, Italian-Puerto Rican singer and composer (d. 2005)
- March 3, 1908 - Birth of Juan Antonio Corretjer, poet, [journalist and independence political activist (d. 1985)
- March 7, 1894 - Birth of Ana María O'Neill, women's rights activist (d. 1981)
- March 9, 1940 - Birth of Raúl Juliá, Golden Globe Award-winning screen and stage actor (d. 1994)
- March 10, 1898 - Puerto Rican leaders of the Cuban Revolutionary Party corresponded with the United States hoping they would include Puerto Rico in the intervention planned for Cuba.
- March 12, 1903 - The University of Puerto Rico is established.
- March 12, 1958 - Death of Luis R. Esteves, the first Puerto Rican to graduate from West Point (b. 1893)
- March 13, 1824 - The Municipality of Aibonito is founded.
- March 14, 1901 - Federico Degetau takes office in Washington, D.C. as the first Resident Commissioner from Puerto Rico.
- March 17, 1995 - Death of Rick Aviles, comedian and actor (b. 1952)
- March 19, 1962 - Birth of Iván Calderón, Puerto Rican Major League Baseball player (d. 2003)
- March 21, 1937 - The Ponce massacre occurred.
- March 22, 1873 - The Spanish National Assembly officially abolished, with a few special clauses, slavery in Puerto Rico.
- March 22, 1979 - Death of René Marqués, renowned short story writer and playwright (b. 1919)
- March 26, 1965 - Birth of Raymond Arrieta, comedian
- March 28, 1969 - Birth of Gisselle (Giselle Ortíz Cáceres), merengue singer
- March 29, 1977 - Birth of Kristina Brandi, professional tennis player
- March 30, 1933 - Birth of Braulio Castillo , telenovela actor