On October 18, 1898, American troops fighting the Spanish-American War raised the United States flag in Puerto Rico formalizing U.S. control of the former Spanish colony. General Nelson A. Miles had landed approximately 3500 U.S. forces on the island in July. Having encountered little resistance, he secured the island on August 12.
Spanish exploration of the island began in 1493 when Christopher Columbus visited during his second journey to the New World. In 1508, Spanish explorer Juan Ponce de León established the first permanent Spanish settlement there at the town of Caparra.
In the early 1880s, Puerto Ricans (at the time under Spanish rule) began to work for independent government. They reached their goal in 1897; however, a year later, control of the island fell into the hands of the United States. Under the provisions of the 1898 Treaty of Paris which ended the Spanish-American War, Spain ceded the island to the United States.
Puerto Rico became a U.S. territory in 1917. Migration from rural areas to metropolitan regions increased during the twentieth century as industry supplanted agriculture in the island economy. Starting in the 1920s, Puerto Ricans began leaving the island to seek employment in cities like New York where they formed communities called barrios.
Since 1952, the Commonwealth of Puerto Rico has been a freely associated state within the federal system of the United States. Puerto Rico's hotly-debated future holds myriad possibilities including statehood, independence, and remaining a commonwealth.