6th Regiment, Mississippi Infantry
6th Infantry Regiment (also called 7th Regiment) was assembled at Jackson, Mississippi, in February, 1861. Its companies were recruited in the counties of Rankin, Quitman, Leake, Scott, Copiah, and Simpson. On April 26, 1865, it surrendered. The field officers were Colonels Robert Lowry and John J. Thornton; Lieutenant Colonels R.R. Bennett, Thomas J. Borden, and A.Y. Harper; and Majors W.T. Hendon and J.R. Stevens. 
The 6th Mississippi Infantry Internet site has a longer history taken from Dunbar Rowland's Military History of Mississippi, 1803-1898.
An extensive history can be found on the 6th Mississippi Infantry Regiment "The Bloody Sixth" Internet site. It also has links to a Muster Roll Index, a Staff Officers and the 6th Mississippi Living History Group.
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.
Information from Military Annals of Mississippi: Military Organizations which entered the Service of the Confederate states of America from the State of Mississippi, by John C. Rietti, Spartanburg, South Carolina: Reprint Company Publishers, 1976. p. 57, FHL 976.2 M2r, inlcudes roster.
- 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 ‘Mississippi 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.
- Mississippi in the Civil War describes many Confederate and Union sources, specifically for Mississippi, 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.
- Rowland, Dunbar, Military History of Mississippi, 1803-1898: taken from the Official and statistical register of the State of Mississippi, 1908 (Spartanburg, South Carolina: Reprint Company).
- Howell, H. Grady, For Dixie Land, I’ll Take My Stand!: A Muster Listing of All Known Mississippi Confederate Soldiers, Sailors, and Marines (Chickasaw Bayou Press, 1998).
- National Park Service, The Civil War Soldiers and Sailors System (accessed 11 January 2011)