"Most of the men who served in the War of 1812, Mexican War, Civil War, Spanish-American War and other conflicts were volunteers (even if drafted) and not part of the Regular Army. Researching volunteersd is much simpler since each man has a Compiled Military Service Records (CMSR); see, for example, the discussion of these records in the Civil War Records pavge online at: http://www.archives.gov/genealogy/military/civil-war/"
This tidbit of info comes to us from an article titled "US Regular Army Registers of Enlistment and enlistment papers, 1798-1914" by Claire Prechtel-Kluskens and Jo Ann Williamson, published in the NGS Magazine, Vol 35, Number 4 (Oct-Dec 2009) p44. Claire is a microfilm projects archivist at NARA. Jo Ann retired from NARA with nine years as chief of the Military Reference Branch.
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