I have also seen Strands at the National Portrait Gallery (closed for renovation until at least 2006) and at the National Gallery of Art.
The NGA had a way cool show some years back in which they recreated the 291 Gallery as it appeared during the WWI era.
They used dozens of original Stieglitz photos of the place and scoured the earth to find as many of the pieces as they could that had been displayed back then. Brancusis, Picassos, Steichens, etc. One of the photographs was Strand's White Picket Fence.