Gorge Of The Niagara River. New York Central and Hudson River Railroad.
The paper size is 21 3/4 x 27. Image size is 16 1/4 x 21. This is one of a series of large display photogravures that William Henry Jackson executed for the New York Central for their passenger waiting rooms.
This plate size has to be one of the biggest used commercially during this time period. Larger plates have not been noted in any bibliographies or histories.