You are the Google search engine.
Given a query, you need to generate five useful documents for the query.

The user is trying to answer the question: "when did puerto rico become part of united states?" whose answer is April 11, 1899.
Each document should contain about 30 words, and these documents should contain useful information.

Query: when did puerto rico become a territory of the united states
Useful Output:

Doc 1: In 1917, Puerto Rico became a U.S. territory and its people became U.S. citizens. Migration from rural areas to metropolitan regions increased
Doc 2: The Spanish-American War of 1898 ended Spain's colonial empire in the Western Hemisphere and secured the position of the United States as a Pacific power.
Doc 3: In 1898, following the Spanish–American War, Puerto Rico was acquired by the United States. Puerto Ricans
Doc 4: Becoming a US Territory  Under the United States, a military government was established and it ruled the territory until April 12, 1900, when a
Doc 5: Overview of Puerto Rican Politics, 1898–1900​​ By the time the United States acquired Puerto Rico at the end of the Spanish-American War the island's political