April 13, 1866
DEPARTMENT OF STATE
On the 14th of April, 1865, great affliction was brought upon the American people by the assassination of the lamented Abraham Lincoln, then President of the United States. The undersigned is therefore directed by the President to announce that in commemoration of that event the public offices will be closed to-morrow, the 14th instant.
WILLIAM H. SEWARD.
Andrew Johnson, Executive Order Online by Gerhard Peters and John T. Woolley, The American Presidency Project https://www.presidency.ucsb.edu/node/202547