The Birds of America
He followed "The Birds of America" with a sequel "Ornithological Biographies". This was a collection of life histories of each species written with Scottish ornithologist William MacGillivray. The two books were printed separately to avoid a British law requiring copies of all publications with text to be deposited in Crown libraries, a huge financial burden for the self-published Audubon. Both books were published between 1827 and 1839.