They are US Citizens.
Puerto Rico is part of the United States. It is called a commonwealth.
It granted Puerto Ricans partial US citizenship status
The 1917 Jones Act designated Puerto Ricans as US Citizens.
Citizens.
Between two and three million that are self identified as Puerto Ricans.
No, having the observatory has NOTHING to do with the necessity for a U.S. passport. I´ll explain to you the little history that I know about Puerto Rico. Puerto Rico was adquired by the U.S. in 1898 after they had won the Spanish-American War in 1898. Later, in the ´50´s (in 1952 I believe), Puerto Rico´s political status was elevated to a "commonwealth/estado libre asociado." Since then, Puerto Ricans have been American citizens just like anyone else born in the continental US. However, Puerto Rico is NOT a state and Puerto Ricans pride themselves in being Puerto Ricans/Boricuas more often than simply Americans. Thus, a passport is not needed for traveling between the US and Puerto Rico.
All puerto ricans are us citizen since 1917 and if they live in the states they have to to pay federal taxes.
For the same reason that some one from New York who moves to California is not Considered an immigrant. Puerto Rico is part of the United States. Puerto Ricans are US citizens by birth since 1917.
If you were asking "Are Puerto Ricans illegal aliens?" that would be a yes AND no answer. Puerto Ricans are considered immigrants because Puerto Rico is not part of the United States (its not one of our 50 states), but it is US territory (we protect them and stuff). :) hope this helped you :)
For employment opportunity.
US citizenship
Many are.