The role of pharmacists and the process of military drug supply in the American Civil War are described. Most raw drugs used in the United States in the mid-1800s were imported. During the Civil War, imports into the North continued, but the Union blockade forced the Confederacy to obtain medicines through means such as smuggling, capture of enemy supplies, and processing of indigenous medicinal plants. Medical supplies for Civil War troops were typically purchased by military physicians called medical purveyors and sometimes by pharmacists serving as acting medical purveyors. In the latter half of the war, U.S. Army medical laboratories, in which many pharmacists were employed, inspected purchases, repackaged supplies bought in bulk, and manufactured medicines from raw materials. The Confederacy also had medical laboratories, which were primarily responsible for manufacturing medicines from indigenous plant material but also inspected drugs that had been smuggled into the South. At a few large Union medical depots, pharmacists called medical storekeepers assumed many of the responsibilities of medical purveyors by receiving, storing, issuing, and accounting for supplies. Noncommissioned officers called hospital stewards assumed diverse duties that included dispensing drugs prescribed by military physicians. Although many hospital stewards were pharmacists or physicians, others had no previous pharmaceutical experience. Civilian pharmacists were employed in the medical laboratories and in military general hospitals. Pharmacists participated in nearly every aspect of military drug supply during the Civil War.