The One Hundred and Ninth Infantry was recruited chiefly of residents of Union county except Company K, which was from Pulaski county. The Regiment was mustered into the United States service September 11, 1862, at which time it was armed with a very inferior gun.

The Regiment remained in camp drilling until the 20th of October, when it was ordered to Cairo; thence it moved to Columbus, Ky., where the companies were separated and assigned to guard duty for two or three weeks, when the Regiment was moved to Bolivar, Tenn., and reported to General Brayman; remained there about two weeks drilling and performing guard duty; was next moved to Moscow, Tenn., and reported to General Quinby; remained there one week; was moved thence in the direction of Holly Springs, with Quinby's Division; at Lumpkin's Mill the Regiment was detached and left there on account of the bad condition of their guns, which were deemed unfit for use in battle. Subsequently the Regiment was moved back to Holly Springs to guard railroad bridges between there and Waterford, a distance of about 10 miles.

On the 1st day of January 1863, the Regiment moved into Holly Springs and reported to General Grant. Soon afterward it was moved to Memphis, where it remained until the last of March performing guard duty; thence it moved to Lake Providence, arriving there April 1. By this time the Regiment was greatly reduced in numbers and because of this it was consolidated with the Eleventh Infantry, where the further history of the service of the men composing the One Hundred and Ninth may be found.