The President’s call for troops only requested one regiment from Mississippi. Volunteers by the hundreds were waiting and eager for the call, and it was no sooner made than Governor Brown was embarrassed by the necessity for selecting out of so many. Finally, it was decided to accept companies from the following counties:
From Hinds - two under Captains Reuben N. Downing and John L. McManus
From Warren - two under Captains George P. Crump and John Willis
From Wilkinson - one under Captain Douglass H. Cooper
From Carroll - one under Captain Bainbridge D. Howard
From Lafayette - one under Captain William Delay
From Marshall - one under Captain James H. R. Taylor
From Yazoo – one under Captain John M. Sharp
From Lowndes and Monroe – one under Captain Alexander K. McClung

They rendezvoused at Camp Brown, near Vicksburg, and organized, choosing one of the state’s representatives in Congress as colonel, a young man of West Point training and considerable experience in the United States service – Jefferson Davis – who resigned his civil office, and proceeded to secure rifles at New York. The brilliant young captain of the Monroe-Lowndes company was chosen lieutenant-colonel and was given command of Camp Brown and ordered to proceed to New Orleans and thence to Point Isabel, at eh mouth of the Rio Grande, where Colonel Davis soon arrived with arms, and spent months in drilling them to efficiency.
The list of officers, non-commissioned officers, musicians, and privates of the First Regiment Mississippi Riflemen, in the war with Mexico (to serve twelve months).
 

Date of enlistment, June 1846:

Field and Staff Officers:

Jefferson Davis – Colonel
Alexander K. McClung – Lieutenant-Colonel
Alexander B. Bradford – Major
Richard Griffith – Adjutant
Seymour Halsey – Surgeon
John Thompson – Assistant Surgeon
Charles T. Harlan – Sgt.-Major
S. Warren White – Quartermaster-sergeant
Stephen Dodds – Principal Musician
Kemp S. Holland – Assistant Commissary

Companies:

Company A - Yazoo - Yazoo Mounted Infantry - Captain John M. Sharp

Company B - Wilkinson - Wilkinson Volunteers - Captain Douglas H. Cooper

Company C - Warren - Vicksburg Southrons - Captain John Willis

Company D - Carroll - Carroll County Volunteers - Captain Bainbridge D. Howard

Company E - Hinds - State Fencibles - Captain John L. McManus

Company F - Lafayette - Lafayette Volunteers - William Delay

Company G - Hinds - Raymond Fencibles - Captain Reuben N. Downing

Company H - Warren - Vicksburg Volunteers - Captain George P. Crump

Company I - Marshall - Marshall Guards - James H. R. Taylor

Company K - Lowndes & Monroe - Tombigbee Volunteers - Captain William P. Rogers