Puerto Rico is defined as a commonwealth of the U.S., in other words, they are more or less like a state. For example, citizens of P.R. are also U.S. citizens and pay some federal, import, social security, etc. taxes. HOWEVER, a point of debate is that they don't pay income tax to the U.S. gov't. Other features of the relationship include the mixture of their militaries and inclusion of Puerto Ricans in the U.S. draft. The Commonwealth of Puerto Rico is a self-governing unincorporated territory of the United States. All citizens of Puerto Rico are citizens of the United States. Puerto Rico has been a US possession since 1898 (Spanish-American War) and has had local self-government, to one degree or another, since 1947.