Excerpts from Books and Wikipedia
"Puerto Rico fell to the United States well over a century ago during the Spanish-American War of 1898. Since the Puerto Ricans had been struggling for some time to free themselves from Spanish imperial rule, this transfer of power was, in their view, only a change from one colonial master to another. As a result, the first half-century of U.S. administration was difficult, and it was not until 1948 that Puerto Ricans were permitted to elect their own governor. When the island’s voters approved the creation of a Commonwealth in a 1952 referendum, Washington, D.C. and San Juan, the seats of government involved, entered into a complicated arrangement. Puerto Ricans are U.S. citizens but pay no federal taxes on their local incomes. Puerto Rico also receives a sizeable annual subsidy from Washington, averaging approximately U.S. $13 billion in recent years. Despite these apparent advantages in the poverty-plagued Caribbean, Puerto Rico has not thrived under U.S. administration. Long dependent on a single-crop economy (sugar), the island based its industrial development during the 1950s and 1960s on its comparatively cheap labor, tax breaks for corporations, political stability . . ."