De Kay served on the staffs of Generals Mansfield, Pope, and Hooker during the Civil War. Partially printed pass from the Headquarters of the Military Department of Washington, dated August 6, 1861, just a few weeks after the First Battle of Bull Run, allowing passage "over the bridges & within the lines" of defense of Washington, DC. On the reverse is a printed loyalty oath that includes "and if ever hereafter found in arms against the Union, or in any way aiding her enemies, the penalty will be death." Signed on the front by De Kay as aide-de-camp with his famously enormous signature - the signature alone measures 1½" by 6"! De Kay's colossal autograph was well-remembered by many people moving within the capital boundaries during the early days of the war. "That fearful signature," one contemporary journalist wrote, " could be read as far away as the Sandwich Islands." Professionally de-acidified and backed. $265.00