This work is a regimental log of the 80th Illinois Volunteer Infantry Regiment documenting its activities in the American Civil War from 27 October 1863 to 17 June 1865. There is no evidence that this memorandum has ever been published before, nor is there evidence that previous Civil War historians knew of its existence. The 80th Illinois Volunteer Infantry Regiment saw substantial action in the war. It traveled over 6,000 miles and was engaged in more than 20 pitched battles. Although the language used in this memorandum is naturally choppy and rough compared to more modern narratives, it will hopefully serve as a useful puzzle piece in the larger history of the regiment, and indeed of the war itself.