Silas T. Grisamore was born in Indiana in 1825 and moved to Louisiana in 1846, settling first in Napoleonville and then in Thibodaux. He engaged in a variety of occupations but found most success as a merchant, selling goods from a flatboat that plied the waterways of the southern part of the state. When the Civil War began, Grisamore enlisted with the Lafourche Creoles, soon to become Company G of the 18th Louisiana Infantry Regiment. Because of his experience as a merchant, much of Grisamore's service during the war was as a quartermaster, first for the 18th Louisiana and later for an infantry brigade and an infantry division.