100th Regiment, Pennsylvania Infantry

Brief History
This regiment was organized at Pittsburg August 31, 1861. It was also known as "The Round Head Regiment". It mustered out July 24, 1865.

For more information on the history of this unit, see:


 * The Civil War Archive section, 100th Regiment Infantry, (accessed 20 September 2012).

Companies in this Regiment with the Counties of Origin
Men often enlisted in a company recruited in the counties where they lived though not always. After many battles, companies might be combined because so many men were killed or wounded. However if you are unsure which company your ancestor was in, try the company recruited in his county first.

The Civil War Soldiers and Sailors database lists 3,282 men on its roster for this unit. Roster.

Field Officers and Staff - See Roster

Regimental Band - See Roster

Company A - Many men were recruited in Washington County - See Roster

Company B - Many men were recruited in Lawrence County - See Roster

Company C - Many men were recruited in Butler County - See Roster

Company D - Many men were recruited in Beaver County - See Roster

Company E - Many men were recruited in Lawrence County - See Roster

Company F - Many men were recruited in Lawrence County - See Roster

Company G - Many men were recruited in Lawrence County - See Roster

Company H - Many men were recruited in Lawrence County - See Roster

Company I - Many men were recruited in Lawrence County - See Roster

Company K - Many men were recruited in Lawrence County - See Roster

Company M - Many men were recruited in Westmoreland County - See Roster

Unassigned Men - See Roster

Regimental History and Roster

 * A Brief History of the One Hundredth Regiment (Roundheads). By Samuel Penniman Bates. New Castle, PA: B Thomas, Book and Job Printer, 1881. Online at: Internet Archive


 * A Brief History of the One Hundredth Regiment (Roundheads), added short sketches of Leasure and Browne . By Samuel Penniman Bates. New Castle, PA: B Thomas, Book and Job Printer, 1881. Online at: FamilySearch Digital Library, Internet Archive


 * Infantryman Pettit: the Civil War Letters of Corporal Frederick Pettit. By William Gillifan Gavin. New York: Avon Books, 1990. Online at: Internet Archive (Regimental Roster -Appendix B)

Other Sources

 * Beginning United States Civil War Research gives steps for finding information about a Civil War soldier. It covers the major records that should be used. Additional records are described in ‘Pennsylvania 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.


 * Pennsylvania in the Civil War describes many sources, specifically for Pennsylvania, and how to find them. These include compiled service records, pension records, rosters, cemetery records, Internet databases, published books, etc.


 * 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.


 * Gavin, William Gilfillan. "Campaigning with the Roundheads: The History of the Hundredth Pennsylvania Veteran Volunteer Infantry Regiment in the American Civil War: the Roundhead Regiment". (Dayton: Morningside House, 1989). . GoogleBooks.WorldCat.


 * Pa-roots gives a history of this regiment with a list of companies and rosters for each company. It lists additional references.


 * Ranger 95 describes the organization of this regiment and its battles. There are rosters for each company. It shows an image of the monument to this regiment.


 * pacivilwaroutlines the history and battles of this regiment. It has rosters for each company. It has some journals and diaries.