I have a personal library of books about 19th century American Landscape painting. This happens to be in a number of them as it was one of the most important paintings of the late part of the century. I recently wrote a big research paper on it.
If you ever want to see it in person, it is hanging at the Autry Museum of Western Heritage in Los Angeles. I've seen it there a few times. Its 5 x 7 feet!