Cuba, 1639.

By the 19th century, the islands had become economic powerhouses, producing hugely profitable sugar, coffee, and tobacco crops. But they were also political powder kegs, as their inhabitants—the descendents of Spanish colonists, free and enslaved Africans, and native islanders—fought to free themselves from Spanish rule. By the end of the century, the people of Cuba were on the verge of independence, and Puerto Rico might have soon followed.

But in 1898, the United States entered the islands and changed their fate forever. War had broken out between the U.S. and Spain, and by its end Spain’s colonies in the Caribbean were under U.S. control. From that point on, the destinies of the two islands diverged dramatically. Puerto Rico would become a U.S. commonwealth, and its people would become U.S. citizens in 1917. Cuba would achieve independence in 1902, but by the end of the century it would come to be defined by its hostile relations with the U.S. and its allies.

In the 20th century, these close but uncertain relationships with the United States would come to affect each island profoundly. They would also help shape two of the most distinctive immigrant experiences in U.S. history.

For a detailed overview of Puerto Rico at the turn of the 20th century, visit “In Search of a National Identity: Nineteenth- and Early Twentieth-Century Puerto Rico.”

For more about Cuba in the same period, visit “The World of 1898: The Spanish-American War.”