We're going to need the Wayback Machine to get to Gautier's today. It once stood at 252 Pennsylvania Avenue; but they've changed the street addresses, and I'm not sure what stands there now.
Brady's Studio was at 352 Pennsylvania Avenue at that time, but I think the numbers got lower as you went uptown. Brady's building still stands and it's in the 600 block, I think, under the new numbering system.
Gautier's may have been where the huge FBI headquarters are now?