According to lasdontrailofhonor.com:

The next monument on the trail is in honor of those who served in the Spanish American War. This war fought for control over Cuba and the Philippines out of fear of a Spanish invasion of the United States and to create a hold on South America. The war ignited after the sinking of the battleship Maine, and with the help of the media, the United States gave Spain the ultimatum to either leave Latin America or face retaliation. Spain and the United States declared war in 1898, beginning ten weeks of one sided victories for the Americans, ultimately annihilating the Spanish troops in South America. Once peace had been declared, the United States gained temporary control over Cuba, as well as indefinite control over Guam, Puerto Rico and the Philippines. The serviceman resembles a member of the 1st United States Volunteer Cavalry, a unit later led by future president Theodore Roosevelt that was nicknamed “The Rough Riders”.