In 1820, John James Audubon decided that he wanted to publish a book with an illustration of every bird in North America.
Eighteen years later, The Birds of America was complete, a collection of 435 hand-colored, life-size prints of nearly 500 bird species, on pages that measured 39 by 26 inches. Today it is considered one of the best ornithological works ever; it includes 25 species discovered by Audubon and six that have gone extinct since its publishing.
Only 119 copies of Audubon's work survive; their beauty and rarity make them highly coveted. According to The Economist, a list of the ten most expensive books ever would include five copies of The Birds of America. So it's not surprising that when a one once owned by the Duke of Portland was auctioned off by Christie's, it was bought for $7.9 million by a private American collector.
The sum was a hefty one, but not quite enough to match the $10 million paid for a different copy in 2010. John James Aududon is considered a founding figure in the field of ornithology and is the namesake of the National Audubon Society, an environmental organization dedicated to conservation.