15th Regiment, Arkansas Infantry (Johnson's) (Confederate)
15th (Gee's-Johnson's) Infantry Regiment was organized at Camden, Arkansas during the late summer of 1861. Six companies were sent to the defense of Fort Henry, then were transferred to Fort Donelson and captured in February, 1862. When exchanged and reorganized, the regiment was assigned to Beall's Brigade, Department of Mississippi and East Louisiana. It fought in some minor engagements at Cross Landing, Greenfield, and Keller's Lane, and later became part of the garrison at Port Hudson where it was captured in July, 1863. This regiment sustained the highest number of casualties of any unit defending the post, eighty-one percent of the 484 engaged. After the exchange, it was not reorganized. 
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.
See : EDWARD G. GERDES, Arkansas Civil War Regiments, Rosters and Muster Rolls, 
- 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 'Arkansas 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.
- Arkansas in the Civil War describes many Confederate and Union sources, specifically for Tennessee, 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.