“American Treasures of the Library of Congress” has a couple of nice pictures you can view online of Niagara Falls in 1846. The pictures were taken by Captain Michael Seymour:
Captain Michael Seymour, commanding officer of the H.M.S. Vindictive, toured the eastern seaboard for fifteen days in July 1846, traveling through Boston, the state of New York, Philadelphia, and finally Washington, D.C. He captured the landscape of a growing republic in the British tradition of topographical draftsmanship. In a letter to his daughter he described Niagara Falls at length, writing, “They are quite terrific to stand near, and contemplate from some, of the points of view either below or overhanging them. I, of course, tried to make a few sketches, but it is impossible to give on paper the Grandeur and immensity they possess. . . .”