1840s
“The Viviparous Quadrupeds of North America” with Bachman
Together with John Bachman Audubon began a book on quadrupeds, agreed back in 1831: he did the illustrations and Bachman wrote the text. By the mid-1840s his sons were doing most of the work (John Woodhouse drew about half of the 150 illustrations), and in 1845 relations with Bachman soured further: Audubon did not supply him with skins from his last collection, his notes or the books Bachman had ordered.
March – November 1843
An expedition up the Missouri to the Rockies
From March to November 1843 Audubon made an expedition up the Missouri River toward the Rocky Mountains, a severe ordeal that undermined his health; he was accompanied by Edward Harris, the taxidermist John Graham Bell, the artist Isaac Sprague and an assistant, Lewis Squires. The expedition yielded fewer new birds than hoped: in a letter to Spencer Baird he reported bringing back 15 new species and some quadrupeds.
1846–1847
Failing sight, dementia and a heart attack
In 1846 Audubon's eyesight suddenly deteriorated: with glasses he could still read but no longer draw. A year later he developed dementia and lost interest in life, and in the spring of 1847 he suffered a heart attack; his sons concealed their father's condition so as not to harm the success of the “Quadrupeds”.

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