However, it was a chance encounter in his youth with a book that inspired Ayer's lifelong investments of time and money that resulted in one of the largest collections of historical and American literature accumulated by the early 20th century.
"[4] In 1860 at the age of nineteen, Ayer headed west to Silver City, Nevada, where he found employment at a quartz mine.
With money saved from this hard labour Ayer was able to move to San Francisco, where he stayed with family friends and got a job at a saw mill, gaining his first experiences in the industry which would later make his fortune.
At roughly twenty years old, this was the first library Ayer had ever seen, and upon reading Conquest of Mexico he describes the experience as one that "seemed to open up an absolutely new world to me".
Within a month, Ayer was in Chicago on business where he happened past a bookseller and negotiated to purchase Prescott's full five-volume set on the conquests of Mexico and Peru.
Ayer was also an early benefactor of the Field Museum of Natural History (FMNH), instrumental in its foundation and serving as its first president.
[12] Ayer himself led in the expansion of the museum's library, in 1894 donating 400 of his own volumes on ornithology and a further 600 he had bought from the collection of Charles Cory.
Ayer continued to expand to the museum library holdings with further purchases of natural history collections in ichthyology and other topics, and donations from his own acquisitions.