Persons born in Puerto Rico on or after Jan. 13, 1941, are automatically citizens of the United States. Anyone born in Puerto Rico before that date but after April 11, 1899, and residing anywhere under U.S. sovereignty as of Jan. 13, 1941, was automatically granted U.S. citizenship.
The obligations and rights held by Puerto Ricans are not quite the same as other citizens of the United States. Puerto Rico is a self-governing commonwealth and doesn't have voting representation in either house of Congress. Its residents cannot vote in U.S. presidential elections while residing on the island, but if they move to one of the 50 states, they can. Puerto Rican men register for the U.S. military draft when they turn 18 years old.