Not sure they would have been at 1st Bull Run ? They would have just begun the process of organizing.
THE THIRTEENTH ALABAMA INFANTRY.
The Thirteenth Alabama infantry was organized at Montgomery,
It was warmly engaged at Seven Pines, May 31 to June 1, 1862, and
in the battles around Richmond, June 26 to July 1, 1862. It also
participated in the Maryland campaign and was engaged in the
battles of Boonsboro, September 15th, and Sharpsburg, September
17th, and was present at Fredericksburg December 13th, but owing
to its position was not engaged.
It was particularly distinguished in the assault upon Hooker at
Chancellorsville, May 1 to 4, 1863, and was superb in its charge
at Gettysburg, where it planted its colors on the crest of the
ridge, suffering frightfully in killed and wounded.
It also took part in the battles of the Wilderness, and in the
numerous engagements around Petersburg, June, 1864, to the
surrender at Appomattox in April, 1865.
Among its killed were: Capt. John D. Clarke, at Mechanicsville,
June 26, 1862; Adjt. John W. Rentz, at Sharpsburg, Mail John T.
Smith, at Chancellorsville; Adjt. L. P. Broughton, at the
Wilderness; Capt. R. M. Cook, at Second Cold Harbor; Lieut. David
R. Staggers, near Bristoe Station.
Among the other field officers were: Birkett D. Fry, afterward
distinguished as a brigadier-general; Col. James: Aiken, Lieut.-
Cols. Julius C. Mitchell, Samuel B. Marks, Reginald H. Dawson,
William H. Betts and Maj. John D. Smith.
Source: Confederate Military History, vol. VIII, p. 97
THE THIRTEENTH ALABAMA INFANTRY. Provenance Reconstruction:
This flag is an Army of Northern Virginia, 3rd wool bunting issue. Flags of this issue were manufactured at the Richmond Depot between July 1862 and May 1864. It was issued to the regiment after the loss of their 2nd wool bunting issue flag at Antietam (Sharpsburg) September 17, 1862. The flag was carried by the regiment at Gettysburg, Pennsylvania where it was nearly captured on the first day (July 1, 1863) during the retreat from McPherson's Ridge.