Considered the "father of American ornithology," Wilson was the greatest American ornithologist before Audubon. Wilson died with the 7th volume in press, and the 8th and 9th volumes were completed by Wilson's friend George Ord, who included a memoir of Wilson in the final volume. Because of the limitation of Wilson's travels and his early death, the work was incomplete, but it was by far the most extensive work about American birds to date, and the color plates set a new standard for works produced in America, even though Wilson's artistry was sometimes crude, and his depictions of birds were stiff and out of scale. The set has been called "the first truly outstanding American color plate book of any type" (Bennett). Digital facsimile of the complete set from the Biodiversity Heritage Library at this link.