Hi Cyndi, Are you sure about the unit in which your ancestor served? According to Ex. Doc No. 62, 30th Congress, First Session, "Letter from the Secretary of War..." (May 4, 1848; pp 32-33), Mississippi did NOT send three regiments to the War. Rather, it sent the following:
1st Regiment of Mississippi Rifles Volunteers for 12 months June 3 1846 to June 1847
2nd Regiment of Mississippi Volunteers for the war. June 12, 1847 to July 1848.
1st Battalion of Mississippi Rifle Volunteers for the war. (5 companies) Sept 1847-Jan 1840 to June 1848.
There was no 3rd Regiment of Mississippi Volunteers recorded.