15th (McRae's-Hobb's-Boone's) Infantry Regiment (also called 21st and Northwest Regiment) was formed in December 1861, using the 3rd Arkansas Infantry Battalion as its nucleus. It took an active part in the battles at Wilson's Creek and Elkhorn Tavern, and on March 11, 1862, contained 10 officers and 168 men. Later the unit moved east of the Mississippi River, fought at Corinth and Hatchie Bridge, then was assigned to M. E. Green's and Dockery's Brigade in the Department of Mississippi and East Louisiana. It sustained 82 casualties at Port Gibson and was part of the garrison captured at Vicksburg on July 4, 1863. When exchanged, the regiment was not recognized, but some of its members joined other Arkansas commands. The field officers were Colonels Squire Boone, James H. Hobbs, and Dandridge McRae; Lieutenant Colonel William W. Reynolds; and Majors D. A. Stuart and William Thompson.