What is the relation between Puerto Rico and the US?

Answer 1

Puerto Rico is an "unincorporated territory" of the United States which according to the U.S. Supreme Court's Insular Cases is "a territory appurtenant and belonging to the United States, but not a part of the United States."

Puerto Rico is subject to the Congress' plenary powers under the territorial clause of Article IV, sec. 3, of the U.S. Constitution. U.S. federal law applies to Puerto Rico, even though Puerto Rico is not a state of the American Union and has no voting representative in the U.S. Congress. Because of the establishment of the Federal Relations Act of 1950, all Federal Laws that are "not locally inapplicable" are automatically the law of the land in Puerto Rico.

Since 1917, people born in Puerto Rico are U.S. citizens. However, federal electoral law does not grant a vote to any citizen who does not live in, or qualify as an absentee resident in, one of the fifty states or the District of Columbia. Thus, people who have always lived in Puerto Rico cannot vote in federal elections, but people born in Puerto Rico and living in a state or in DC can vote.

(WIKI)