Puerto Rico became part of the United States in 1898 , after the Spanish–American War, when Spain ceded the island to the U.S. in the Treaty of Paris. It has been under U.S. control ever since, first under military rule and later as a civil territory.

Key dates at a glance

  • 1898 – U.S. troops invade Puerto Rico during the Spanish–American War; Spain later cedes the island to the U.S. in the Treaty of Paris.
  • 1898–1917 – Puerto Rico is governed as a U.S.-controlled colony/possession, not yet with formal territorial and citizenship status as later defined by law.
  • 1917 – The Jones–Shafroth Act makes Puerto Rico a formal U.S. territory and grants U.S. citizenship to Puerto Ricans born on or after April 25, 1898.
  • 1952 – Puerto Rico adopts its own constitution and becomes a self-governing U.S. commonwealth (Estado Libre Asociado), still under U.S. sovereignty.

So if you’re asking “when did Puerto Rico become part of the United States?” most historians point to 1898 , when Spain ceded the island to the U.S. and U.S. control formally began. If you mean “when did it become a U.S. territory with U.S. citizenship for residents?” , the key date is 1917 with the Jones–Shafroth Act.

Information gathered from public forums or data available on the internet and portrayed here.