Wow, these are awesome. Click on them for greater detail because they are pretty amazing. Sorry I just wasted at least 30 minutes of your time at work! Thank you Library of Congress.

UPDATE: If you like these, you will also be fascinated by this photo of the Ebbitt House Hotel in 1889.

UPDATE 2: GoDCer Brian over at National Journal has posted some great contemporary photos to go along with these. Check them out here.