Puerto Ricans are Americans, but have a vague legal status that will impair the island's recovery. Here's everything you need to know:

Why is Puerto Rico part of the U.S.?
Puerto Ricans had no choice in the matter. A Spanish colony since Ponce de León established a settlement there in 1508, Puerto Rico had just acquired voting rights and its own constitution in 1898 when the U.S. invaded the island during the Spanish-American War. The generals promised the locals — descendants of Spanish colonists, former slaves, and indigenous Taino — a free future, and many sided with the U.S. against Spanish rule. But once the war was over, and Spain had ceded the island along with the Philippines and Guam, the U.S. did not recognize the local parliament and instead set up a colonial administration. The U.S. president appointed governors, who chose their own cabinets. Puerto Rico was effectively a colony and officially a territory.

Why isn't it a state?
For racial reasons. Most U.S. territories did become states; Oklahoma, for example, became a territory in 1890 and a state in 1907. The difference was that Oklahoma was settled largely by English-speaking whites, who displaced the Native Americans. Starting in 1901, the same Supreme Court that had approved "separate but equal" segregation for black Americans, in the infamous Plessy v. Ferguson case, ruled in a series of decisions that Puerto Rico and other territories that were "inhabited by alien races" were not ready to be governed by "Anglo-Saxon principles." Puerto Rico was declared an "unincorporated territory" — different from the Alaskan and Hawaiian incorporated territories — and the path to statehood was closed off. Unlike Plessy v. Ferguson, the Insular Cases, as these rulings are known, were never overturned.

Can Puerto Ricans vote?
Puerto Ricans are U.S. citizens from birth, thanks to a law passed in 1917 partly aimed at allowing them to serve in the Army during World War I. But they have no voting representation in Congress, and they can't vote for president unless they move to the mainland. While they don't pay federal income taxes, Puerto Ricans do pay some $3 billion annually to the federal government in Medicare, Social Security, and other taxes. They are eligible for U.S. public assistance programs, and receive about $20 billion a year in such aid, with 40 percent of the poverty-stricken population getting food stamps. After World War II, when colonies around the world were gaining independence, Congress allowed Puerto Rico to write and adopt its own constitution, with its own bill of rights. That constitution calls Puerto Rico a commonwealth, but the legal status of that term was never quite nailed down, leaving it in limbo.

Why does that hurt the island?
The biggest problem is that Puerto Rico can't fully control its own economy. During the first few decades under U.S. administration, authorities imposed a colonial structure of sugar plantations, which hurt other local industries. In the 1970s and '80s, the territory benefited from U.S. tax exemptions that encouraged pharmaceutical firms and other corporations to locate there, but when Congress started phasing those out in 1996, manufacturing declined and the economy tanked. The territory's elected leaders began making up the shortfall by issuing bonds, creating a ballooning debt of more than $70 billion. Bankruptcy rules that allow cities such as Detroit to restructure debt don't apply to Puerto Rico, and rather than change that, Congress passed the PROMESA law last year, creating an oversight board that took financial control entirely away from local authority and imposed severe austerity.

What status do Puerto Ricans want?
They are divided. Some want statehood, some independence, and others a commonwealth option that would allow them to retain U.S. citizenship but enable them to make their own treaties with foreign countries. There's no majority for any of the options. The latest vote was this past June, but most factions boycotted. The result was a 97 percent vote for statehood — but with turnout of just 23 percent. The devastation from Hurricane Maria, though, may change the island forever. Already, the Puerto Ricans on the mainland — some 5 million — outnumbered the island's population of 3.4 million. With 80 percent of people still lacking power, 30 percent without water, and thousands of businesses destroyed, many Puerto Ricans with the means to leave are fleeing to the mainland.

What's Puerto Rico's future?
Right now, it looks grim. Puerto Ricans are furious at what they see as a slow FEMA response, as well as at President Trump's insinuation that they, unlike hurricane victims in Texas and Florida, will have to pay back any aid they receive. Activists are putting pressure on Congress to relax the rules that deny Puerto Rico the recourses a state would have. The Jones Act, which bars foreign ships from delivering goods to the island, has been temporarily waived, but could be repealed. Debt restructuring is under discussion. Puerto Rico Gov. Ricardo Rosselló warns that without significant aid to rebuild the island's infrastructure, reduce its debt, and revive its economy, there will be a mass exodus. "You're not going to get hundreds of thousands of Puerto Ricans moving to the States," Rosselló said. "You're going to get millions."

The Navy's toxic legacy
For decades, the U.S. Navy had a major base on Puerto Rico, and used the territory's nearby Vieques Island as a bombing range. The Roose­velt Roads Naval Station, opened by FDR in 1940, was a launchpad for the U.S. invasions of the Dominican Republic in 1965, Grenada in 1983, and Haiti in 1994, and it boosted Puerto Rico's economy. But Vieques residents said the relentless bombing was destroying the environment, and after a stray bomb killed a civilian and prompted major protests, the Navy closed the base in 2004. Vieques is now a Superfund site contaminated with lead, Agent Orange, and depleted uranium. Its 9,000 residents have rates of cancer that are 27 percent higher than those for the rest of Puerto Rico, and testing reveals that many people's bodies have toxic levels of lead, arsenic, and mercury. But the U.S. gov­ern­ment denies any connection between the bombing and the high cancer rates, saying its own studies revealed "no apparent public health hazard."