In 2000, Julius K. Hunter and Friends invested in a collection of Genealogical Resources in Microfilm and Microfiche for the St. Louis County Library. Many of those films have been digitized and are now available through FamilySearch or Fold3. This includes the Organization Index to Pension Files of Veterans Who Served Between 1861 and 1900 (NARA Microfilm Publication T289)
Important to Note: Rolls 540-579 covered Colored Troops