20th Regiment, US Infantry (Regular Army)
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"Compendium of the War of the Rebellion" by Frederick H. Dyer contains no history for this unit. 
Regimental and Company Histories and Rosters
- Beginning United States Civil War Research gives steps for finding information about a Civil War soldier or sailor. It covers the major records that should be used. Additional records are described in 'Florida in the Civil War' and 'United States Civil War, 1861 to 1865' (see below).
- National Park Service, The Civil War Soldiers and Sailors System, is searchable by soldier's name and state. It contains basic facts about soldiers on both sides of the Civil War, a list of regiments, descriptions of significant battles, sources of the information, and suggestions for where to find additional information.
- United States Civil War, 1861 to 1865 describes and explains United States and Confederate States records, rather than state records, and how to find them. These include veterans’ censuses, compiled service records, pension records, rosters, cemetery records, Internet databases, published books, etc.
- Union Regular Army in the Civil War describes Union sources, specifically about the Union Regular Army in the Civil War, and how to find them.
- National Park Service, The Civil War Soldiers and Sailors System, (accessed 6 December 2010).