It's obviously a baking powder explosion. Those are the worst. Either that, or substandard masonry with an inadequate foundation.

That's why you never lean back in your chair.

I'm surprised no one has made that joke!

Turnbuckle stars!

Crawlspace gin? I am curious about the narrow area with the wood piled on the barrel and the two wall-mounted bedposts. To what purpose, other than 1920 being the start of Prohibition.

[A hallway or closet? Barrels were the cardboard boxes of their day. - Dave]

for the looting to begin. Anyone need an enema bag?

contains a ghastly apparition of a person with a bloodied face and neck, possibly dressed in a nightshirt. Or not.

[Or an ad for soap or shampoo. - Dave]

Looks like one of the cigar store customers was blowing onion rings.

This is the northeast corner of F Street and New Jersey Avenue NW, viewing the (former) facade on F Street.

UPDATE: A bit of sleuthing suggests that the large "M. []" at left was originally "M. LEWIS," whose name appears in a full-page May 1, 1919 Star ad listing hundreds of shopkeepers participating in a special offer for a Quaker Oats double-boiler. We can even see some of the ill-fated oats in the photo above.

FURTHER UPDATE: The collapse occurred on the morning of Oct. 16, 1919. Attached below are clippings from the Washington Times (washed-out image) and Evening Star.

The culprit left a print.

I'm guessing the person who lives just above the store was a little embarrassed with his or her enema contraption hanging on the bathroom wall for all to see.

It would appear that the accommodations are themselves transient.

Washington is full of these 19th century structures and every now and then a wall on one (and more rarely, the entire structure) will simply collapse. And it isn't all that unusual to see cracks of various sorts in their walls. Whether due to settlement or some flaw in the mortar used in that era I can't say.

Probably due to water seepage for 100 years then the weak wall gave way on a windy day. It happens. Curious what that wooden barrel is used for in the plumbing chase ?

An inducement that could be added to the Rooms Furnished sign. I am guessing a simple wall collapse. No sign of earthquake or explosion. Most of the store goods are still on the shelves, even the cans stacked on the top shelf.

If so afflicted, it's never good to reside above a cigar emporium.