Why arent puerto ricans living in the us considered immigrants?

Puerto Ricans who live in the United States are considered American citizens and not immigrants. This is because Puerto Rico is a territory of the United States and has been since the Spanish-American War in 1898. As such, Puerto Ricans are considered to be birthright citizens of the United States. Puerto Rico is not a state, but its people are still citizens, which is why Puerto Rican people may live in the mainland US without legal status issues that immigrants from other countries may face.