Final answer:
The Spanish-American War was sparked by the sinking of the U.S.S. Maine in Havana Harbor.
Step-by-step explanation:
The spark that ignited the beginning of the Spanish-American War was the sinking of the U.S.S. Maine. On February 15, 1898, the battleship Maine exploded in Havana Harbor, Cuba. The incident was widely blamed on Spain, although the exact cause of the explosion remains a mystery to this day. The sinking of the U.S.S. Maine eventually led to the United States declaring war on Spain.
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