From what I have read I am under the impression that the whole 3rd Vaughn's (later to become Lillard's Mounted) Tennessee Infantry Regiment, PACS (Provisional Army, Confederate States of America)left Winchester, Va on Thursday the 18th of July for Manassas Junction arriving at the Junction on Sunday July 21 and was under fire by 1 o'clock in the first battle of Manassas that day. (10 Companies in Regiment) The Regiment was part of a brigade then being commanded by General E. Kirby Smith.

Company Roles filled from men of a particular Tennessee County when organized at Knoxville, Tn - May 29, 1861.

Company A from Knox County
Company B from Monroe County
Company C from Polk County
Company D from Polk County
Company E from Blount County
Company F from Monroe County
Company G from McMinn County
Company H from Monroe County
Company I from Meigs County
Company K from Sullivan County
(No Company J shown)
(Info from page 137 of "Military Annals of Tennessee"-'Regimental Histories and Memorial Rolls.'
And from page 179 of "Tennesseans In The Civil War, Part I"

Hope this helps you. Good Luck and God Bless.