Fished this photograph below from some
Russian website. It has "Architect of the Capitol" watermark on it, but I can not find any official source of this photo.
Interesting that stone blocks were individually packed. And blocks were numbered, which suggests a kit house. It could also suggest that the stone is not natural, if those are indents. Even if it's a lime or sandstone, the indents still do not make sense, for a simple pencil would suffice.
Also if this indeed is the DC Capitol they are building... who knows what that brick building they are covering with the stone blocks was? I certainly hope it's not the center piece of the Capitol. That one was destroyed around 1812, and at the time of its repairs there was no photography yet.
If it's one of the wings being built, the question remains, what is the old brick building?
Basically, what are they building, where is this photograph on the official website, and what year is this?
Here is one additional photograph.