7th Regiment, Mississippi Infantry
7th Infantry Regiment was organized at Corinth, Mississippi, in April, 1861 with men from Marion, Amite, Pike, Franklin, Lawrence, Yalobusha, Holmes, and Covington counties. The unit was briefly consolidated with the 9th Mississippi Regiment in December, 1863. On April 26, 1865, it surrendered. The field officers were Colonels William H. Bishop, E.J. Goode, Hamilton Mayson, and A.G. Mills; Lieutenant Colonels R.S. Carter and Benjamin F. Johns; and Major Henry Pope. 
The 7th Mississippi Volunteer Infantry Internet site has links to a history, rosters, photos and gravesites.
The 7th Mississippi Infantry Internet site has a longer history taken from Dunbar Rowland's Military History of Mississippi, 1803-1898.
Regiment Companies with the County 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.
Company B - (Bogue Chitto Guards) - raised in Pike County
Company C - (Amite Rifles) - raised in Amite County also known as Company A
Company D - (Jeff Davis Sharpshooters) - raised in Marion County also known as Company E
Company F - (Marion’s Men) - raised in Marion County also known as Company I
Company G - (Goode Rifles) - raised in Lawrence County also known as Company F
Company H - (Dahlgren Rifles) - raised in Pike County
Company I - (Covington Rifles, aka Covington Rangers) - raised in Covington County
Company K - (Quitman Rifles) - raised in Franklin County and Holmes County
Information from Military Annals of Mississippi which entered the service of the Confederate States of America from the State of Mississippi, by John C. Rietti, Spartenburg, South Carolina: Reprint Company Publishers, 1976, p. 59, FHL book 976.2 M2r includes 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.
- 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), FHL book 976.2 M2
- 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), FHL book 976.2 H2
- National Park Service, The Civil War Soldiers and Sailors System (accessed 11 January 2011)