Final answer:
The Hawaiian Islands were not gained by the U.S. as a result of the Spanish-American War; they were annexed during the war because of strategic interests and economic opportunities.
Step-by-step explanation:
The territory that was NOT gained by the U.S. as a result of the Spanish-American War is the Hawaiian Islands. While territories such as Guam, Puerto Rico, and the Philippines were ceded to the United States following the Spanish-American War, Hawaii was annexed by the United States during the war but not as a direct result of it. Hawaii's path to U.S. annexation was influenced by both strategic interests and its position as a gateway to Asian markets, leading to its annexation in 1898 and subsequent territorial status in 1900.