Was William McKinley an imperialist?

McKinley may or may not have been an imperialist. This is a matter of some debate among historians.
McKinley helped give rise to the American Empire by expanding the nation's borders to Guam, Hawaii, the Philippines, and Puerto Rico. The Philippines was later granted independence. McKinley also presided over the Spanish American war and the military occupation of Cuba—though America never claimed actual ownership of the island.
The Spanish American War offers an insight into the debate about whether McKinley had imperial ambitions. McKinley entered into negotiations with Spain prior to the war in an attempt to gain independence for the Cuban people. This followed from reports of concentration camps in Cuba that had been implemented by the Spanish. America invaded Cuba after talks broke down between America and Spain. Puerto Rico, Guam, and the Philippines were ceded to America during the peace negotiations.
If McKinley's stated goals were sincere, then his territorial expansion was done largely to remove Spanish control over island populations within the American sphere of influence, undermining the argument that he was an imperialist. However, Hawaii is a different story that appears more imperial.