Between 1898 and 1932 the U.S. government intervened militarily thirty-four times in ten nations in the Caribbean and Central America to extend and protect its economic interests. U.S. influence in the Circum-Caribbean was not new, however, and stretched back to the early nineteenth century. In 1823 President James Monroe proclaimed in the Monroe Doctrine that the United States would keep European influence out of Latin America. This bold assertion established Latin America as part of the U.S. sphere of influence. U.S. interventions in Latin America were also a byproduct of the manifest destiny ideal of consolidating national territory from the Atlantic to the Pacific. Often the easiest way to connect the two sides of the continent was through Latin America.

The California gold rush of the 1840s created pressure to move people and goods quickly and inexpensively between the eastern and western parts of the United States decades before its transcontinental railroad was completed in 1869. It was cheaper, faster, and safer to travel to the east or west coast of Mexico and Central America, traverse the continent where it was narrower, and continue the voyage by sea. The first railroad constructed in Central America served exactly this purpose. Built with U.S. investment, the Panama Railway, which opened in 1855, retraced the path that Spaniards had used to cross from their colony in Peru to the Atlantic.

Planters and politicians in the U.S. South, who faced pressure from Northern abolitionists against the westward territorial expansion of the slave regime, responded by seeking opportunities to annex new lands in Latin America and the Caribbean. They eyed Cuba, the Dominican Republic, El Salvador, and Nicaragua. In Nicaragua, just after the Panama Railway was completed, Tennessean William Walker employed a mercenary army to depose the government and install himself as president (1856–1857). One of his first acts was to reinstate slavery. He was overthrown by armies sent from Costa Rica, El Salvador, and Honduras.

By the end of the nineteenth century U.S. involvement in Latin America had intensified, first through private investment and then through military force. In 1893 a group of New York investors formed the Santo Domingo Improvement Company, which bought the foreign debt of the Dominican Republic and took control of its customs houses (the government’s major source of revenue) in order to repay investors and creditors. After the government propped up by the U.S. company fell, President Theodore Roosevelt intervened, introducing what would be known as the Roosevelt Corollary to the Monroe Doctrine, which stated that the United States, as a civilized nation, would correct the “chronic wrongdoing” of its neighbors, such as failure to protect U.S. investments.

To this end, in 1903 and 1904 Roosevelt deployed Marines to the Dominican Republic to protect the investments of the Santo Domingo Improvement Company and other U.S. firms. Marines occupied and governed the Dominican Republic again from 1916 to 1924. The occupying forces organized a National Guard through which a notoriously violent and corrupt dictator, Rafael Trujillo, rose to power and ruled from 1930 to 1961. He ruled with the support of the United States, and when he eventually defied the United States, he was assassinated by rivals acting with the encouragement of the Central Intelligence Agency.

Versions of the Dominican Republic’s experience played out across the Circum-Caribbean. U.S. Marines occupied Haiti from 1915 to 1934 and Nicaragua from 1912 to 1934. These military occupations followed a similar pattern of using military force to protect private U.S. companies’ investments in banana and sugar plantations, railroads, mining, port facilities, and utilities. During repeated occupations, the U.S. military ruled like dictators and violently suppressed protest and resistance. And as U.S. forces departed, they left power in the hands of dictators who served U.S. interests. These dictators governed not through popular consent but through force, corruption, and the support of the United States.