In 1898, during the Spanish–American War, Puerto Rico was invaded and subsequently became a possession of the U.S. The first years of the 20th century were marked by the struggle to obtain greater democratic rights from the U.S.

The Foraker Act of 1900 established a civil government, ending rule by American generals and the Department of War. A U.S. Supreme Court ruling, Ortega v. Lara, involving the Foraker Act and referring to the island as "the acquired country", soon affirmed that the U.S. Constitution applied within its territory and that any domestic Puerto Rican laws which did not conflict with it remained in force.

The Jones Act of 1917 made Puerto Ricans U.S. citizens. The Jones act paved the way for the drafting of Puerto Rico's Constitution and its approval by Congress and Puerto Rican voters in 1952. Puerto Rico is one of five territories with less representation in the Federal government, along with the Federal District.

From Library of Congress.