After the Spanish-American War ended in 1898, Puerto Rico was transferred from Spanish to American sovereignty, beginning a dramatic transformation of the island’s government, economy, and daily life. The Treaty of Paris, signed on December 10, 1898, formally ceded Puerto Rico to the United States, and Congress was given full authority to determine the civil rights and political status of the island’s inhabitants. What followed was a rapid sequence of military rule, new civil government, economic upheaval, and a legal limbo that in many ways persists today.
The Treaty of Paris and the Transfer of Power
Under the treaty’s terms, Spain surrendered Puerto Rico (along with the Philippines and Guam) to the United States. Spanish-born residents on the island could choose to stay or leave, keeping their property rights either way. Those who stayed had one year to formally declare allegiance to Spain before a court; anyone who didn’t was automatically considered to have adopted the nationality of the territory. Critically, the treaty did not make Puerto Ricans U.S. citizens. Instead, it punted the question entirely, stating that “the civil rights and political status of the native inhabitants” would be determined by Congress at some future date.
Two Years of Military Government
From 1898 to 1900, the U.S. Army governed Puerto Rico directly. Military officers took on roles that went well beyond security, functioning as public health officials, urban planners, and municipal administrators. In Ponce, one of the island’s largest cities, an Army surgeon organized a board of health almost immediately after occupation. Streets and buildings were cleaned, disinfected, and fumigated. The city’s water supply was improved by dredging silt from the reservoir pond and installing a filter on the aqueduct. The old cemetery, where bodies were already being buried in layers, prompted plans for a new one. The city prison was disinfected and repaired, and the Army ordered smallpox vaccine from the mainland to begin compulsory immunization of all citizens.
Hospitals were modernized with new plumbing and refrigeration. These were real, tangible improvements, but they were imposed from above by a military authority with no democratic input from the Puerto Rican population.
The Foraker Act and Civil Government
In 1900, Congress passed the Foraker Act, replacing military rule with a civil government. The new structure included a governor and an executive council appointed by the U.S. president, a House of Representatives with 35 elected members, a Supreme Court, and a nonvoting Resident Commissioner in Congress. Puerto Ricans could now elect local representatives, but the most powerful positions on the island were filled by appointees from Washington. The governor could veto legislation, and Congress retained ultimate authority over the island’s affairs.
This arrangement gave Puerto Rico a veneer of self-governance while keeping real power in American hands. The island was neither a state nor an independent nation, and its residents had no vote in the presidential elections that determined who would appoint their governor.
The Insular Cases: A Legal Limbo
Starting in 1901, a series of Supreme Court decisions known as the Insular Cases defined Puerto Rico’s constitutional status in a way that still shapes life on the island. The Court held that the United States could rule Puerto Rico and other territories largely without regard to the Constitution. The key distinction was between “incorporated” territories (on a path to statehood, where the full Constitution applied) and “unincorporated” territories like Puerto Rico, where it did not.
In practical terms, this meant Congress could extend or withhold constitutional protections as it saw fit. Puerto Ricans lacked voting rights in federal elections, full access to federal benefits programs, and the ability to fully govern themselves. As one legal scholar put it, unincorporated territories existed in a kind of limbo, where “the Constitution applied differently, if at all.” This doctrine has been criticized repeatedly, but as recently as 2022, the Supreme Court upheld a ruling that residents of Puerto Rico were not entitled to receive Supplemental Security Income benefits, partly because Congress has not required them to pay most federal income, gift, estate, and excise taxes.
U.S. Citizenship in 1917
Nearly two decades after the war, President Woodrow Wilson signed the Jones-Shafroth Act on March 2, 1917, granting Puerto Ricans U.S. statutory citizenship. The act also reorganized the island’s government into three branches (executive, judicial, and legislative) and established a bill of rights for residents. But the governor and the U.S. executive branch retained the power to veto or override any law passed by the Puerto Rican legislature.
The timing was notable. The act became law just one month before the United States entered World War I, and Puerto Rican men were now eligible for the military draft. Citizenship brought certain rights and protections, but it did not bring statehood, full representation in Congress, or a vote for president.
Economic Transformation Through Sugar
The war’s economic consequences were enormous. Under Spanish rule, Puerto Rico’s sugar industry had been relatively modest. After 1898, a presidential proclamation in 1901 brought Puerto Rico into the U.S. customs territory, giving the island the same tariff protections that mainland sugar producers enjoyed. American sugar companies invested heavily. The area devoted to sugarcane tripled, and farm sizes grew as land was consolidated.
By the mid-1920s, Puerto Rico’s raw sugar production had climbed to 661,000 tons, up from about 440,000 tons at the start of the decade. Sugar exports reached roughly 600,000 tons by the end of 1927, accounting for nearly 60 percent of the island’s total exports. Over 40 percent of production was controlled by just three corporations. This concentration of land and wealth displaced small farmers and created a plantation economy deeply dependent on a single crop and on access to the U.S. market. Puerto Rico’s economy was no longer diversified; it was tethered to American corporate interests and U.S. trade policy.
Public Health: Progress and Crisis
The early decades of American rule brought both public health investment and stark evidence of ongoing suffering. Death rates spiked dramatically in the years immediately following the war, reaching 40.8 per 1,000 people in 1900, up from 24.6 in 1893. The causes were intertwined: poverty, malnutrition, tropical diseases, and the disruption of war itself.
Anemia was the leading cause of death on the island at the turn of the century. Puerto Rico’s own Sanitation Board attributed it to malnutrition, malaria, and climate, and did little to address it. In 1899, an Army physician named Bailey Ashford identified the real culprit: an intestinal parasite that entered the body through the feet when they came in contact with contaminated soil. Ashford created an Anemia Commission in 1904 to diagnose, research, and treat the disease. By 1907, 33 anemia control centers had been established across the island. Over the following decades, death rates gradually fell, reaching 18.6 per 1,000 by 1930. But these improvements were uneven, and they came alongside an economic system that kept much of the population in poverty.
A Territory, Not a State
The fundamental outcome of the Spanish-American War for Puerto Rico was a change in colonial rulers. Spain’s flag came down and the American flag went up, but the island’s residents had little say in the transition and even less control over what followed. The legal framework established in the early 1900s, from the Foraker Act to the Insular Cases, created a political status that was deliberately ambiguous: Puerto Rico belonged to the United States but was not fully part of it. Residents were eventually granted citizenship but not the full rights that came with living in a state. The economy was reshaped to serve mainland interests, and public health improved in some measurable ways while deeper structural inequalities persisted. Many of these tensions remain unresolved more than 125 years later.