* Commemorates the anniversary of the day in 1952 when Puerto Rico became a commonwealth with the proclamation of their constitution. ** The United States had acquired the island after the Spanish-American war, and did not allow self-government until the 1950's, when their constitution was written. ***Also known as Commonwealth Day, or Occupation Day in commemoration of the US troops landing on the island on this day in 1898 (shagtown.com)