The Thirtieth Regiment was raised exclusively from the citizens of the 10th Congressional District comprised of Allen, DeKalb, Elkhart, Kosciusko, La Grange, and Noble Counties. It was organized at Fort Wayne in Allen County, using Camp Allen as a home base. The men were mustered in on the 24th day of September, 1861, with Colonel Sion S. Bass as the commanding officer. The regiment as a whole was mustered into the 19th United States Infantry on the 29th of September.

The regiment, which consisted of ten companies, left Camp Allen on the 30th of September for Indianapolis. Leaving there on the 7th of October, they progressed to Camp Neven in Kentucky, and on the 9th reported to General Rousseau.

Soon after joining the brigade of General Alexander McCook, the regiment moved with General Don Carlos Buell's army to Munfordsville and Bowling Green, Kentucky. Then in March of 1862 they marched to Nashville, Tennessee.

From Nashville they moved South to Shiloh and participated in the battle there on the 7th of April. Colonel Sion Bass was severely wounded during the Battle of Shiloh. He died several days later at Paducah, only seven months since his date of commission had passed. Lieutenant Colonel Joseph B. Dodge was promoted to Colonel. Shiloh, being the first true battle in which the Thirtieth had actually fought, took its toll in killed and wounded:

The Thirtieth marched with the army to Corinth, Mississippi and took part in the siege that occurred there, then moved on through northern Alabama and Tennessee to Kentucky with General Buell's forces.