What Puerto ricans celebrate in their parade?

I know that immigrants from many countries have their national parade in the U.S. cause celebrate their independence, but Puerto Rico isn't a country, it belong to the U.S. since the first world war, they are U.S. citizen and there are more Puerto Ricans in the U.S. that in the Island. when i always ask to Puerto Ricans why they have a parade or many of them cuz they have about 3 or 4 per year, they don't even know what to tell me, sometimes they get mad, lol. SO PLEASE MY PUERTO RICANS FELLAS, CAN YOU ANSWER THIS QUESTION WITHOUT THE GHETTO ATTITUDE? PLEASE? THANKS