Final answer:
The USS Maine was sent to Havana Harbor to observe and protect American interests during Cuban instability. After its explosion in 1898, the media blamed Spain, inciting the Spanish-American War despite later evidence suggesting an internal accident.
Step-by-step explanation:
The USS Maine was in Havana Harbor in the late 1890s to protect U.S. interests and citizens during a period of instability in Cuba. At the time, Cuba was one of Spain's remaining colonies, where a war for independence was occurring, drawing the attention of the United States due to significant American investments and trade ties to the island.
On February 15, 1898, the battleship mysteriously exploded, which the sensationalist American press attributed to Spanish aggression, though later investigations suggested an internal accident involving the ship's munitions near the engine room as the more likely cause.
Nonetheless, the tragedy led to escalated tensions and the rallying cry, 'Remember Maine, to Hell with Spain!', contributing to the onset of the Spanish-American War when the U.S. declared war on Spain in April 1898.