MEDIA Show Media Credit: Library of Congress Prints & Photographs DivisionOriginal Author: UnknownCreated: ca. 1864Medium: Wet collodion glass-plate negativeUnion Colonel Samuel Chapman ArmstrongSamuel Chapman Armstrong wears the insignia of a Union colonel in this glass-plate photograph, taken around 1864. Armstrong was promoted to the rank of colonel in October 1864 and was later breveted brigadier general.FEATURED INSamuel Chapman Armstrong (1839–1893)