Hello there! As your question is related to looking for identification/information regarding military personnel, our Guide on Military Identification may be of use to you. It provides a number of different resources, including how to request service records from a number of national agencies around the world, as well as graphical aids to assist in deciphering rank, unit, and other forms of badges or insignia. While the users here may still be able to lend you more assistance, hopefully this will provide a good place to start!

It appears to me to be an American Naval officers Uniform of the Spanish-American War era, for comparison here is a photo of Admiral Dewey. My guess is that he is wearing a Lieutenants uniform as the insignia on his sleeve resembles that of a lieutenants from earlier periods.

As noted above, it is possible that this is a Spanish-American War Naval uniform, but the belt buckle and the sword hilt make me think this is really some kind of fraternal uniform, of which there were many, such as Masons, Knights of Columbus, Knights of Pythias, etc. Neither belt nor sword really look military. The sword looks awfully Masonic to me, but I am not an expert on these fraternal groups.