Having gained international renown with The Birds of America, during the 1840s John James Audubon embarked upon an ambitious plan to illustrate and publish the animals of North America. At that time, American mammals had received far less study, and the available literature was often contradictory. He collected specimens sent to him, toured Canada to canvass for subscriptions in 1842, and made a final expedition up the Missouri River in 1843 to collect specimens and notes. The Viviparous Quadrupeds of North America was issued as lithographs in both large portfolio in 1845–48 and a smaller, multivolume edition in 1854. Audubon was then well into his fifties and beginning to be challenged by health issues. His eyesight was failing, and he was experiencing symptoms of what today would be diagnosed as Alzheimer’s disease. By 1846, he had completely given up painting, leaving the responsibility for completing the artwork to his son John Woodhouse Audubon. About half of the original drawings for the work were by Audubon; the rest were by his son. Audubon died on January 27, 1851, at his home on the Hudson River, before his friend, the Reverend John Bachman, had completed the text. John T. Bowen, then one of the finest lithographers in the country, was engaged by the Audubons and their partner Bachman. In all, 150 plates were issued resulting in approximately 300 sets. In spite of the fact that the Quadrupeds did not include a number of the mammals that were originally considered, the plates and Bachman’s accompanying text was a landmark event in American natural history.