Located about a thousand miles from Florida in the Caribbean Sea, Puerto Rico is a United States territory—but it's not a state. U.S. citizens who reside on the island are subject to federal laws, but can't vote in presidential elections. Why? The answer lies in the island's long colonial history—one that arguably continues to this day.

Puerto Rico had been a Spanish colony since the 16th century, but hundreds of years of repression, taxation, and poverty took their toll. By the 19th century, an independence movement sprang up on the island. Though Spanish forces quickly quelled an armed insurrection in 1868, the country tried to diffuse tensions by allowing the island more independence.

But a few decades of relative autonomy came