What is this?
This is a painting of the Niagara Falls by an American artist called Louis Mignot.
Mignot was showing the Falls from the Canadian side in this painting. Although Niagara was already a very popular tourist destination, Mignot purposely concentrates on the natural spectacle, eliminating tourists, scenic viewpoint stations, the nearby hotels, etc.
It was painted in 1866, when photography began to really become popular, and when artists started becoming aware about the ways that memories recorded through painting differ from those recorded through photography.