M.M.White undertaker WashingtonDC Matthias M. White undertaker of Washington , DC Fisk and Raymond metallic coffins

I like to highlight known burials by MM White this one is August 1857 at Congressional Cemetery

Commodore John Thomas Newton (May 20, 1793 – July 28, 1857) was an officer in the United States Navy who commanded several ships over a period of decades, undertaking missions in the Caribbean and leading the first crossing of the Atlantic by an American steam-powered warship. He was court-martialed following a fire that destroyed that vessel, but his suspension from service was remitted by President John Tyler, after which Newton commanded Pensacola Navy Yard and the Home Squadron for periods. He died while serving in his last post as president of a Naval Court of Inquiry. 

Death 

Newton died on July 28, 1857, in Washington, D.C., at age 64, of apoplexy, while visiting the residence of Charles Winder.[1] The Brooklyn Daily Eagle reported at the time of his death that Newton "considered Brooklyn as his home", and that he "had a large circle of relatives and friends in this city".[35] The Washington Evening Star reported that it had "stopped the press" with their edition of the day half-worked off to add the announcement of his death.[1] Volunteer companies of the District of Columbia were ordered to attend his funeral.[1] The members of the three Naval Courts of Inquiry met thereafter and appointed a committee to draft resolutions commemorating Newton, which were published in The Washington Union and transmitted to Newton's family.[34] He was buried at the Congressional Cemetery. Burning of the USS Missouri

This happened on MM White same block infront of Capital building in 1861. In the confusion that followed Wednesday’s desecration of the Capitol, it was widely reported that the last time the building was stormed was in 1814. That overlooked a desperate day in 1861, nearly as lethal to democracy. On Feb. 13, a mob gathered outside the Capitol and tried to force its way in to disrupt the counting of the electoral certificates that would confirm Abraham Lincoln’s election three months earlier. LINK

The great Streets of Washington blog has a

Congressional Cemetery Burials in My Tree by Nancy on Scribd

 M.M. White and E.C. Merriam (his son-in-law MM daughter Helen is married to ECM ) attest to a black man (newspaper says colored) John Reed's will in 1867.

He names Gilson Brown as his executor and leaves him $50 and leaves balance of his property to his son J.J. (John James) Reed of Jefferson County, VA and his cousin, Susan Moore of DC.

His will, I would love to more about who Mr Reed was or find his descendants.