The political status of Puerto Rico is that of an unincorporated territory of the United States. As such, the island is neither a sovereign nation nor a U.S. state. Because of that ambiguity, the territory, as a polity, lacks certain rights but enjoys certain benefits that other polities have or lack. For instance, in contrast to sovereign nations, Puerto Rico does not have voting rights in its federal legislature nor in electing its federal head of government. But, in contrast to U.S. states, Puerto Ricans are not subject to federal income taxes. The political status of the island thus stems from how different Puerto Rico is politically from sovereign nations and from U.S. states.

What's the best answer to this question: is puerto rico legally part of the united states?
yes