When Spain surrendered at the end of the Spanish-American War in 1898, it ceded three territories to the United States: the Philippines, Guam, and Puerto Rico. Each of these three islands has taken a different course in the years since, the Philippines becoming a sovereign nation, Guam and Puerto Rico remaining territories of the United States. Puerto Rico, however, has stood out among all American territories for its close relationship with the mainland. The US Congress reorganized that relationship, passing the Jones-Shafroth Act, which was officially signed into law on March 2, 1917.
The Jones-Shafroth Act, bearing the names of Rep. William Atkinson Jones and Sen. John Shafroth who sponsored the legislation, established multiple norms of governance in Puerto Rico. From then on, there would be a Senate of Puerto Rico, similar to the senates and houses governing the states. It also ratified a bill of rights for the island territory and declared Puerto Rican bonds exempt from federal, state, and local taxes. Most notably, though, it granted American citizenship to all Puerto Ricans born on or after April 11, 1899.
For Puerto Ricans, and all Americans, this last point was momentous because two months later, the US Congress began drafting male citizens into the military for World War I. Many Puerto Ricans had opposed the Jones-Shafroth Act for this very reason. Now legally US citizens, Puerto Rican males found themselves subject to conscription. In all, more than 18,000 Puerto Ricans served in the US military over the year and a half of wartime that followed.
Three years after the first Jones Act, a second Jones Act was up for debate. This one, officially the Merchant Marine Act of 1920 introduced by Sen. Wesley Jones (unrelated to William Atkinson Jones), was to set the rules of cabotage of American ports. Under the rules of the 1920 Jones Act, any ship transporting goods by water from one US port to another (including ports in the then-territories of Hawaii, Alaska, Guam, and once again, Puerto Rico) would have to fly a US flag, operate under US ownership, and employ crews of US citizens and US permanent residents.
In practice, the second Jones Act served to protect US maritime and labor interests, affording US citizens and US residents a higher degree of freedom when navigating commerce along the coasts. Like the first Jones Act, though, it proved contentious among Puerto Ricans. More than ninety years later, the Government Accountability Office continued to research the impact of the Merchant Marine Act of 1920 on the Puerto Rican economy, testing the hypothesis that restrictions on cabotage had led to higher prices on imports.
Although the Government Accountability Office concluded that it could not prove or disprove any negative effects of the second Jones Act on Puerto Rico, it waived the rules of the Act after Hurricane Maria. Citizenship, as laid out in the first Jones Act, has over time become far less controversial, and in November 2020, Puerto Ricans voted 52% to 47% in favor of US statehood. The long-term ramifications of that vote remain unclear, but only in the wake of the two Jones Acts, such a vote has been possible at all.