Exhibit | Aug. 3, 2021

American Civil War: Union Code Book

Although entitled Cipher for Telegraphic Correspondence, this book is actually a code book. It was used by Union General Joseph Hooker's code clerk and is one of the few books whose provenance is known. Important names, places, and military terms have two different code names. A code changes a word or phrase into a different word, phrase, or number group; a cipher substitutes each individual letter for a different letter, number, or symbol.