The National Archives microfilm project has greatly enhanced the ability to successfully research the Post Civil War era.
This is especially important for African-Americans (Americans with African-mixed heritage), because of the brief existence of The Bureau of Refugees, Freedmen and Abandoned Lands, a government agency.
In this article, Reginald Washington explains the types of records available and mentions their content and value in genealogical research. ¹

¹Washington, Reginald. "Black Family Research: Records of Post Civil War Federal Agencies at the National Archives." Reference Information Paper 108. National Archives and Records Administration. Washington, D.C. [2001] 07 August 2005. [http://www.archives.gov/publications/ref-info-papers].