Final answer:
The slogan "Remember the Maine and To Hell with Spain" refers to the rallying cry that followed the explosion of the USS Maine in Havana Harbor in 1898, which led to the Spanish-American War when the incident was blamed on Spain by the American press.
Step-by-step explanation:
The slogan "Remember the Maine and To Hell with Spain" is deeply rooted in the events leading up to the Spanish-American War in 1898. The USS Maine, one of the newest American navy battleships, was sent to Havana, Cuba, to protect U.S. interests and citizens during the Cuban fight for independence. An explosion destroyed the Maine on February 15, 1898, killing over 250 American sailors. Although more recent investigations suggest the explosion was an accident, likely caused by internal combustion due to the proximity of gun powder to hot boilers, the incident was widely attributed to a Spanish mine by the sensationalist press of the era, known as yellow journalism. This event galvanized American public opinion and led to war cries against Spain with the rallying cry emerging in newspapers becoming "Remember the Maine!" Congress declared war on Spain shortly after, on April 25, 1898, in response to public outcry and perceived Spanish aggression.
Although President McKinley had sought to avoid war, the explosion of the USS Maine and subsequent popular demand for action contributed to a shift in foreign policy. This event is often seen as a significant catalyst for the declaration of war against Spain which ultimately ended Spanish control in the Caribbean and the Pacific, leading to Cuban independence and the annexation of Puerto Rico, Guam, and the Philippines by the U.S.