After the Spanish-American War , Spain and the United States signed the Treaty of Paris (1898) , by which Spain ceded Puerto Rico , The Philippines, and Guam to the United States for the sum of $20 million. Under the same treaty, Spain relinquished all claim of sovereignty over Cuba. Theodore Roosevelt, who had fought in the Spanish-American War and had some sympathies with the independence movement, succeeded McKinley as U.S. President in 1901 and abandoned the treaty. Cuba gained formal independence from the U.S. on May 20, 1902, as the Republic of Cuba. Under Cuba's new constitution, the U.S. retained the right to intervene in Cuban affairs and to supervise its finances and foreign relations. Under the Platt Amendment, the U.S. leased the Guantánamo Bay naval base from Cuba.

The 1903 lease agreement, while it recognized that the Republic of Cuba held ultimate sovereignty over Guantánamo Bay, gave to the United States "complete jurisdiction and control" of the area for coaling and naval stations. The lease is a transgrassion against the sovereingty of Cuba.

Since 2002, the naval base has a military prison, the Guantanamo Bay detention camp, for persons acused to be unlawful combatants captured in Afghanistan, and in Iraq and in other places. The mistreatment of some prisoners, and their denial of protection under the Geneva Conventions, has been a source of international controversy. In his first campaign to the presidency of the US Barak Obama promised to close Guantanamo but up to now it is still open.