November 8, 1884
We were able to determine from the Providence Board of Trade Journal (vol. 2, p.94, 1891) that Blackstone Hall was on the corners of Washington and Snow Streets in downtown Providence. And that it could accommodate 500-600 people. We could not identify a specific address.
We do have a copy of a glass plate negative of Blackstone Hall which locates it at Washington and Acorn Sts. In the photo we believe the hall is the building with the cupola as it was described as "architecturally excellent" in that same Board of Trade mention.
I attach a scan of the image and of the newspaper clipping announcing Twain's lecture which appeared in the Providence Journal, Monday, 3 Nov 1885, p. 5.
The Hall was first re-purposed for office space in the 1890's and we believe it has long since been torn down because the current location is a sea of parking lots.
Librarian, The Reference Staff
Rhode Island Historical Society
121 Hope Street
Providence, RI 02906