Locals know that you can find all kinds of interesting things at Eastern Market, a farmer's maket and bazaar on Capitol Hill. Eastern Market is one of the District's micro melting pots, where one sees shoppers of all stripes mingling with Hill politicos in their native environment. As an aside, I'll note that Capitol Hill residents simply do not leave the house—not even to pick up the newspaper—in anything less formal than slacks and a blazer.
Whenever I drop by Eastern Market, I usually head straight for the butcher's counter (they sell seriously good cuts of brisket), but from time to time I browse their bins of old photographs, maps, and architectural drawings. SAAM staffer Cassandra Good stopped by recently and discovered a stereograph image of the old Patent Office Building (which houses the Smithsonian American Art Museum and the National Portrait Gallery).
Senior Art Historian Richard Murray estimates that the stereograph was taken in the late 1890s; the presence of stairs leading up to the building indicate that the image cannot have been taken more recently than the 1930s.
For comparison's sake, SAAM staffer Michael Edson took a picture from F Street to capture the Patent Office Building at the same angle today. Currently the building is closed for renovation, but when it reopens in July 2006, the F Street entrance will again serve as the primary entrance. The stairs won't be restored, however, unless F Street is elevated by 12 feet or so. The National Portrait Gallery Web site hosts an architectural history of the building, and some gorgeous pictures can be found here.
If we were judging these two images in a vacuum, I'd say that over the last century photographic technology has changed more than Washington, D.C. That was nearly not the case for this building: In the 1950s, the historic Patent Office was slated for demolition in order to build a parking lot.
UPDATE: I originally posted a draft here instead of the slightly touched-up version you see now. Sorry, I ran into a version-control snafu, but it's fixed.