The correct answer is that after the end of the Spanish-American War, the United States leased Guantanamo Bay from Cuba.
The Naval Base in Guantánamo Bay was established in 1898, when the United States militarily occupied the island after defeating Spain in the Spanish-American War. The government of the United States obtained a perpetual lease that began on February 23, 1903, with the signature by Tomás Estrada Palma, first president of the Republic of Cuba, of the Cuban-American Treaty.
