The foregoing notice from the heads of the Executive Departments of the Government informs you what a signal calamity has befallen us in the death of the President of the United States, and the prominent part assigned you in those funeral honors which may bespeak a nation's respect to the memory of a departed patriot and statesman, whose virtue and talents as a citizen and soldier had achieved illustrious services, and whose sudden death has disappointed the expectation of still more important benefits to his country.
With a view to carry into effect the views of these high officers of Government in a manner befitting the occasion and honorable to the militia corps of this District, I request the general and field officers, the general staff, and the commandants of companies to assemble at my house to-morrow, Tuesday, April 6, precisely at 10 o'clock, to report the strength and equipment of the several corps of the militia and to receive final instructions for parade and arrangement in the military part of the funeral procession.
The commandants of such militia corps from the neighboring States as desire to unite in the procession are respectfully invited to report to me as soon as practicable their intention, with a view to arrange them in due and uniform order as a part of the general military escort.
The detail of these arrangements, to which all the military accessories, both of the regulars and militia, are expected to conform, will be published in due time for the information of all.
For the present it is deemed sufficient to say that the whole military part of the procession, including the regular troops of every arm and denomination and all the militia corps, whether of this District or of the States, will be consolidated in one column of escort, whereof Major-General Macomb, Commander of the Army of the United States, will take the general command, and Brigadier-General Roger Jones, Adjutant-General of the Army of the United States, will act as adjutant-general and officer of the day
Maj. Gen., Comdg. the Militia of the District of Columbia.
William Henry Harrison, District Orders Online by Gerhard Peters and John T. Woolley, The American Presidency Project https://www.presidency.ucsb.edu/node/200484