In September 1861, after the start of the Civil War, Smith joined the 4th Rhode Island Infantry, where he became First lieutenant and quartermaster under General Parke. He took part in Burnside's North Carolina Expedition and participated in the battles of Roanoke, New Bern, and Fort Macon. He returned to Rhode Island in Fall 1862, once again working for Sackett, Davis &amp; Co, where he eventually became superintendent. In 1870 he partnered with Samuel W. Saxton of New York to form Saxton, Smith &amp; Co, which made solid gold chains. He was also president of the United Wire and Supply Company.