There are some great sources including www.spanamwar.com www.nara.gov (order the military records)
My GrGrandfather's obit mentioned his affiliation as a SAW veteran with a Camp in the Lawrence, MA area.I asked more about that at the www.spanamwar.com site and received this very informative response: >My Question: He was also belonged to the Stephen J. Ryan Camp of Spanish American War Veterans (?).
www.spanamwar.com webmaster reply: This would have been the USWV or United Spanish War Veterans. This was a private organization for veterans of the Spanish American War and the Philippine American War, like the American Legion or VFW of today. Their local posts were called "Camps" and were named after a prominent deceased veteran of the war...often a local hero.